Method and apparatus for enhanced radio link control transmission for extended reality in a wireless communication system

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. The disclosure relates to a method and transmitting device (101) for handling enhanced RLC transmit operation for XR. The method includes receiving the discard indication at RLC layer from upper layer to discard at least one RLC SDU associated with the SN. Further, the method includes abandoning or stopping the transmission or retransmission of at least one RLC SDU, segment of the RLC SDU, and RLC data PDU, when the discard indication is received for the at least one corresponding RLC SDU from the upper layer.

Description

METHOD AND APPARATUS FOR ENHANCED RADIO LINK CONTROL TRANSMISSION FOR EXTENDED REALITY IN A WIRELESS COMMUNICATION SYSTEM

[0001] Proposed embodiments in this disclosure relate to a wireless communication system. More particularly, the disclosure relates to enhanced Radio link Control (RLC) transmit operation for Extended Reality (XR) in the communication network system.

[0002] Considering the development of wireless communication from generation to generation, the technologies have been developed mainly for services targeting humans, such as voice calls, multimedia services, and data services. Following the commercialization of 5G (5th generation) communication systems, it is expected that the number of connected devices will exponentially grow. Increasingly, these will be connected to communication networks. Examples of connected things may include vehicles, robots, drones, home appliances, displays, smart sensors connected to various infrastructures, construction machines, and factory equipment. Mobile devices are expected to evolve in various form-factors, such as augmented reality glasses, virtual reality headsets, and hologram devices. In order to provide various services by connecting hundreds of billions of devices and things in the 6G (6th generation) era, there have been ongoing efforts to develop improved 6G communication systems. For these reasons, 6G communication systems are referred to as beyond-5G systems.

[0003] 6G communication systems, which are expected to be commercialized around 2030, will have a peak data rate of tera (1,000 giga)-level bit per second (bps) and a radio latency less than 100μsec, and thus will be 50 times as fast as 5G communication systems and have the 1 / 10 radio latency thereof.

[0004] In order to accomplish such a high data rate and an ultra-low latency, it has been considered to implement 6G communication systems in a terahertz (THz) band (for example, 95 gigahertz (GHz) to 3THz bands). It is expected that, due to severer path loss and atmospheric absorption in the terahertz bands than those in mmWave bands introduced in 5G, technologies capable of securing the signal transmission distance (that is, coverage) will become more crucial. It is necessary to develop, as major technologies for securing the coverage, Radio Frequency (RF) elements, antennas, novel waveforms having a better coverage than Orthogonal Frequency Division Multiplexing (OFDM), beamforming and massive Multiple-input Multiple-Output (MIMO), Full Dimensional MIMO (FD-MIMO), array antennas, and multiantenna transmission technologies such as large-scale antennas. In addition, there has been ongoing discussion on new technologies for improving the coverage of terahertz-band signals, such as metamaterial-based lenses and antennas, Orbital Angular Momentum (OAM), and Reconfigurable Intelligent Surface (RIS).

[0005] Moreover, in order to improve the spectral efficiency and the overall network performances, the following technologies have been developed for 6G communication systems: a full-duplex technology for enabling an uplink transmission and a downlink transmission to simultaneously use the same frequency resource at the same time; a network technology for utilizing satellites, High-Altitude Platform Stations (HAPS), and the like in an integrated manner; an improved network structure for supporting mobile base stations and the like and enabling network operation optimization and automation and the like; a dynamic spectrum sharing technology via collision avoidance based on a prediction of spectrum usage; an use of Artificial Intelligence (AI) in wireless communication for improvement of overall network operation by utilizing AI from a designing phase for developing 6G and internalizing end-to-end AI support functions; and a next-generation distributed computing technology for overcoming the limit of UE computing ability through reachable super-high-performance communication and computing resources (such as Mobile Edge Computing (MEC), clouds, and the like) over the network. In addition, through designing new protocols to be used in 6G communication systems, developing mechanisms for implementing a hardware-based security environment and safe use of data, and developing technologies for maintaining privacy, attempts to strengthen the connectivity between devices, optimize the network, promote softwarization of network entities, and increase the openness of wireless communications are continuing.

[0006] It is expected that research and development of 6G communication systems in hyper-connectivity, including person to machine (P2M) as well as machine to machine (M2M), will allow the next hyper-connected experience. Particularly, it is expected that services such as truly immersive eXtended Reality (XR), high-fidelity mobile hologram, and digital replica could be provided through 6G communication systems. In addition, services such as remote surgery for security and reliability enhancement, industrial automation, and emergency response will be provided through the 6G communication system such that the technologies could be applied in various fields such as industry, medical care, automobiles, and home appliances.

[0007] Extended Reality (XR) encompasses a range of immersive technologies, including Virtual Reality (VR), Augmented Reality (AR), and Mixed Reality (MR). The XR applications demand a communication system framework that supports high data rates, very low latency, and power-efficient connectivity to deliver seamless user experiences.

[0008] In the context of communication networks, the Radio Link Control (RLC) layer is a layer-2 sub-layer responsible for various data plane processing functions. These functions include the transfer of upper layer Protocol Data Units (PDUs), error correction through Automatic Repeat Request (ARQ), segmentation and reassembly of RLC Service Data Units (SDUs), re-segmentation of RLC segments, duplicate detection, RLC SDU discard, RLC reestablishment, and protocol error detection.

[0009] Despite the robust functionalities provided by the RLC layer, existing procedures for RLC SDU discard present inefficiencies when applied to XR applications. The XR applications are dependent on the timely and synchronized transmission of frames, also known as PDU Sets, rather than on the transmission of individual IP packets. Typically, an IP packet is mapped one-to-one to a Protocol Data Convergence Protocol (PDCP) SDU and subsequently to an RLC SDU. This mapping does not align well with the frame-based transmission requirements of the XR applications.

[0010] Further, the current RLC SDU discard procedure cannot be executed once an RLC SDU or any of its segments have been submitted to lower layers, such as the Medium Access Control (MAC) layer. This limitation hinders the ability to efficiently manage the transmission and discard of data, leading to potential delays and reduced performance in XR applications.

[0011] It is desired to address the above-mentioned disadvantages or other short comings or at least provide a useful alternative.

[0012] The principal object of the embodiments disclosed herein is to enhance RLC transmit operation for the XR in a communication network system. The disclosure enables an efficient approach to achieve low latency and reliable data transfer for the XR.

[0013] Yet another object of the disclosure is to support low latency retransmissions for XR services.

[0014] Yet another object of the disclosure is to provide an efficient RLC mechanism to achieve quicker retransmissions and to avoid increasing transmission resource burden.

[0015] Yet another object of the disclosure is to ensure abandonment of transmission and retransmission of discarded SDU or SDU segment at RLC.

[0016] Yet another object of the disclosure is to perform a sequence number re-association at RLC.

[0017] Yet another object of the disclosure is to update the TX-Next-ACK state variable at RLC.

[0018] Yet another object of the disclosure is to handle discard for a large number of SDUs and to avoid HFN un-synchronization.

[0019] Yet another object of the disclosure is to indicate a successful discard to the upper layer at RLC.

[0020] Yet another object of the disclosure is to prioritize transmission at RLC.

[0021] Yet another object of the disclosure is to update the TX-Next-State variable for Unacknowledged Mode (UM) RLC.

[0022] Yet another object of the disclosure is to handle Negative Acknowledgement (NACK) for discarded SDU at RLC.

[0023] Yet another object of the disclosure is to handle retransmission count and to avoid radio link failure.

[0024] In an aspect, the objectives are achieved by providing a method for handling RLC transmission for XR in a communication network system. The method includes receiving by a transmitting device a discard indication at the RLC layer from the upper layer to discard at least one RLC SDU associated with a Sequence Number (SN). Further, the method includes abandoning or stopping by the transmitting device transmission or retransmission of at least one RLC SDU, segment of the RLC SDU and RLC data PDU when the discard indication is received for the at least one corresponding RLC SDU from the upper layer.

[0025] In an embodiment, the method includes transmitting by the transmitting device an indication to the upper layer of a successful discard of the at least one RLC SDU associated with the SN when the at least one RLC SDU is successfully discarded.

[0026] In an embodiment, the method includes setting by the transmitting device Transmission-Next-Acknowledgement parameter to the SN of the first RLC SDU for which a positive acknowledgment has not been received and a discard indication is not received from the upper layer.

[0027] In an embodiment, the method includes performing by the transmitting device re-association of the SN of the at least one RLC SDU after discarding the at least one RLC SDU or a segment of the RLC SDU when the at least one pending RLC SDU or a segment of pending RLC SDU is not transmitted to lower layers. Further, the method includes reassigning by the transmitting device the SN of the at least one discarded RLC SDU to the at least one RLC SDU that is not indicated to be discarded from the upper layer.

[0028] In an embodiment, the method includes skip prioritizing by the transmitting device at least one AMD PDU that contains previously transmitted RLC SDUs or RLC SDU segments that are indicated for discard from upper layer (e.g., PDCP) for transmissions over AMD PDUs that contain not previously transmitted RLC SDUs or RLC SDU segments.

[0029] In an embodiment, the method includes updating by the transmitting device Transmission-Next parameter to increment by one when a segment of the RLC SDU that maps to the last byte of RLC SDU is discarded and is yet not contained in the Unacknowledged Mode Data (UMD) PDU and at least one other segment of the same RLC SDU is contained in the UMD PDU and has been submitted to the lower layer.

[0030] In an embodiment, the method includes determining by the transmitting device whether a negative acknowledgment (NACK) for the at least one RLC SDU or the segment of RLC SDU is received from a receiving device. Further, the method includes retransmitting by the transmitting device the at least one RLC SDU or the segment of the RLC SDU for which the NACK is received if the SN of the corresponding RLC SDU falls within the range TX_Next_Ack <= SN <= the highest SN of the AMD PDU among the AMD PDUs submitted to the lower layer and if the discard indication is not received from the upper layer for the RLC SDU.

[0031] In an embodiment, the method includes performing by the transmitting device when the discard indication is received for the at least one RLC SDU from the upper layer at least one of skip retransmission of the at least one RLC SDU for which the NACK is received. Also, the method includes skip incrementing Retransmission count for the at least one corresponding RLC SDU. Also, the method includes skip considering the Retransmission count that is exceeding a preconfigured maximum retransmission threshold value. Also, the method includes skip indicating to the upper layer that the maximum retransmission has been reached for the at least one RLC SDU.

[0032] In an embodiment, the method includes updating by the transmitting device the Transmission-Next-Acknowledgement parameter based on the sequence number of the discarded RLC SDUs when the number of discarded RLC SDUs is greater than half of a transmission window.

[0033] In an embodiment, the upper layer is at least one of a Packet Data Convergence Protocol (PDCP) layer.

[0034] In an embodiment, the lower layer is at least one of a Medium Access Control (MAC) layer.

[0035] In an embodiment, the transmitting device is at least one of a UE or network entity.

[0036] In another aspect, the objectives are achieved by providing a transmitting device for handling RLC transmission for XR in a communication network system. The transmitting device isat least one of an UE and a network entity. The transmitting device includes a processor and an RLC transmission controller communicatively coupled with the processor. The RLC transmission controller receives a discard indication at the RLC layer from the upper layer to discard at least one RLC SDU associated with a Sequence Number (SN). Further, the RLC transmission controller abandons or stops transmission or retransmission of the at least one RLC SDU, the segment of the RLC SDU, and RLC data PDU when the discard indication is received for the at least one corresponding RLC SDU from the upper layer.

[0037] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications can be made within the scope of the embodiments herein.

[0038] Aspects of the disclosure are to address at least the above-mentioned problems and / or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the disclosure is to provide efficient communication methods in a wireless communication system.

[0039] These and other features, aspects, and advantages of the present embodiments are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:

[0040] Fig. 1 is a block diagram of a transmitting device to handle RLC transmission for XR in a communication network system according to embodiments disclosed herein.

[0041] Fig. 2 is a flow diagram that illustrates a method for handling RLC transmission for XR in a communication network system according to embodiments disclosed herein.

[0042] Fig. 3 is a flow diagram that illustrates an enhanced RLC transmit operation to handle acknowledgment at the transmitting side of the AM RLC entity for XR according to embodiments disclosed herein.

[0043] Fig. 4 is a flow diagram that illustrates an enhanced RLC transmit operation to handle SDU discard at the transmitting side of the AM RLC entity for XR according to embodiments disclosed herein.

[0044] Fig. 5 is a flow diagram that illustrates an enhanced RLC transmit operation to handle SDU discard at the transmitting UM RLC entity for XR according to embodiments disclosed herein.

[0045] Fig. 6 is a structure of a user equipment (UE) according to embodiments disclosed herein.

[0046] Fig 7 is a structure of a network entity according to embodiments disclosed herein.

[0047] Aspects of the disclosure are to address at least the above-mentioned problems and / or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the disclosure is to provide a terminal and a communication method thereof in a wireless communication system.

[0048] It may be noted that, to the extent possible, like reference numerals have been used to represent like elements in the drawing. Furthermore, those of ordinary skill in the art will appreciate that elements in the drawing are illustrated for simplicity and may not necessarily have been drawn to scale. For example, the dimensions of some of the elements in the drawing may be exaggerated relative to other elements to improve the understanding of aspects of the disclosure. Further, the elements may have been represented in the drawing by conventional symbols, and the drawings may showonlythose specific details that are pertinent to understanding the embodiments of the disclosure so as not to obscure the drawing with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

[0049] As is traditional in the field, embodiments are described and illustrated in terms of blocks that carry out a described function or functions. These blocks, which are referred to herein as managers, units, modules, hardware components, or the like, are physically implemented by analog and / or digital circuits such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits, and the like, and may optionally be driven by firmware and software. The circuits, for example, may be embodied in one or more semiconductor chips or on substrate supports such as printed circuit boards and the like. The circuits constituting a block may be implemented by dedicated hardware or by a processor (e.g., one or more programmed microprocessors and associated circuitry) or by a combination of dedicated hardware to perform some functions of the block and a processor to perform other functions of the block. Each block of the embodiments may be physically separated into two or more interacting and discrete blocks without departing from the scope of the proposed method. Likewise, the blocks of the embodiments may be physically combined into more complex blocks without departing from the scope of the proposed method.

[0050] The SDU discard procedure at the PDCP layer involves the discard of the PDCP SDU when the associated timer expires or when the successful delivery of a PDCP SDU is confirmed by the peer PDCP entity, such as through a PDCP status report. When the PDCP SDU or PDCP PDU has already been submitted to the RLC layer for transmission, a discard indication is given to the RLC layer.

[0051] For XR applications, the existing RLC SDU discard procedure may not be effective. The XR applications are more tightly coupled with frame (also termed as PDU Set) transmission rather than with IP packet transmission, which is typically one-to-one mapped to the PDCP SDU and thereby to the RLC SDU. Further, the RLC SDU discard procedure cannot be pursued when an RLC SDU or a segment thereof has been submitted to the lower layers (e.g., MAC layer). Therefore, there is a need for an enhanced RLC transmit operation to support efficient RLC SDU discard.

[0052] Referring now to the drawings, and more particularly to Figs. 1-5 where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments.

[0053] Fig. 1 is the block diagram of the transmitting device to handle RLC transmission for XR in communication network system, according to embodiments disclosed herein.

[0054] The transmitting device (101) is a device that sends or propagates the signals either via a medium that can be a wired or wireless. For example, the transmitting device (101) can include, but not limited to a User Equipment, Consumer Electronics (such as Mobile Phones and Smartphones), Tablets, Wearable Devices, Television, Computing Devices (such as Laptops, Notebooks, Desktops, Workstations, etc.), IoT Devices, Automotive Systems (such as connected cars, Autonomous Vehicles, Vehicle-to-Everything (V2X) communication devices, etc.), Enterprise Devices such as robotics, Specialized Equipment (such as Medical Devices, Public Safety Devices, etc.), Media Devices (such as Gaming Consoles, Streaming Devices, etc.).

[0055] In an embodiment, the transmitting device (101) can be a network side device such as but is not limited to Base Stations (such as macro cells, small cells, femtocells, picocells in 4G, 5G or 6G) for wireless communication, Antennas and RF Units (e.g., MIMO, beamforming) to enhance signal coverage and data throughput, Core Network Equipment (e.g., MMEs, S-GWs, P-GWs in 4G; AMFs, UPFs in 5G; network nodes in 6G) for data routing, mobility, and session control, Network Function Virtualization (NFV) and Software-Defined Networking (SDN) for dynamic resource allocation and scalability, Edge Computing Nodes (e.g., MEC servers) for low-latency processing, Backhaul and Transport Equipment (e.g., fiber-optic links, microwave relays, Ethernet switches) to connect base stations to the core network, Network Management Systems (NMS) and Operation Support Systems (OSS) for network configuration, fault management, and optimization, Radio Network Controllers (RNCs) in 3G, Distributed Units (DUs), and Centralized Units (CUs) in 5G, Network Slicing Components for virtualized resource allocation, Security elements (e.g., Firewalls, IDS, AAA Servers) for secure communication.

[0056] Examples of the wireless communication network system include, but are not limited to, Cellular Networks (such as 2G, 3G, 4G, 5G, Beyond 5G (B5G) / 6G, or advanced cellular networks), Local Area Networks (LANs) (such as Wi-Fi, Li-Fi, etc.), Personal Area Networks (PANs) (such as Bluetooth, Zigbee, Z-Wave, etc.), Wide Area Networks (WANs) (such as Satellite Communication Networks, Long Range Wide Area Network, Narrowband IoT, Low-bandwidth communication for IoT, etc.), Metropolitan Area Networks (MANs), Machine-to-Machine (M2M), Ad Hoc and Mesh Networks, Emerging and Advanced Networks.

[0057] The transmitting device (101) includes a processor (103), a memory (105), an I / O interface (107), and an RLC transmission controller (109). Furthermore, the processor (103) of the transmitting device (101) communicates with the memory (105), the I / O interface (107), and the RLC transmission controller (109). The processor (103) is configured to execute instructions stored in the memory (105) and to perform various processes. The processor (103) can include one or a plurality of processors, can be a general-purpose processor such as a central processing unit (CPU), an application processor (AP), or the like, a graphics-only processing unit such as a graphics processing unit (GPU), a visual processing unit (VPU), and / or an Artificial Intelligence (AI) dedicated processor such as a neural processing unit (NPU).

[0058] Furthermore, the memory (105) of the transmitting device (101) includes storage locations that can be addressed through the processor (103). The memory (105) is not limited to volatile or non-volatile memory and can include one or more computer-readable storage media. Non-volatile storage elements such as magnetic hard disks, optical discs, floppy discs, flash memories, EPROM, or EEPROM memories can also be included in the memory (105). Further, the memory (105) of the transmitting device (101) can store various information received from the upper layer at the transmitting device (101). The transmitting device (101) can store several pieces of information such as discard indication and the like.

[0059] The I / O interface (107) transmits information between the memory (105) and external peripheral devices, which are input-output devices associated with the transmitting device (101). The I / O interface (107) receives various information from the upper layer of the transmitting device (101).

[0060] The RLC transmission controller (109) communicates with the I / O interface (107) and the memory (105) for handling RLC transmission for extended reality in a communication network system. The RLC transmission controller (109) is an innovative hardware that is realized through the physical implementation of both analog and digital circuits, including logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive and active electronic components, as well as optical components.

[0061] The RLC transmission controller (109) performs at least one of abandonment of transmission or retransmission at RLC, sequence number re-association at RLC, updates TX-NEXT_ACK state variable at RLC, successful discard indication to upper layer, transmission prioritization approach, update of TX_Next_state variable for UM RLC, handling NACK for discarded SDU, handling RETX_COUNT and handling discard for large number of SDUs. The RLC transmission controller (109) enables an efficient approach to achieve low latency and reliable data transfer for XR and improves network performance.

[0062] The RLC transmission controller (109) receives the discard indication at the RLC layer from the upper layer to discard at least one RLC SDU associated with the SN. Further, the RLC transmission controller (109) abandons or stops transmission or retransmission of the at least one RLC SDU, the segment of the RLC SDU, and RLC data PDU when the discard indication is received for the at least one corresponding RLC SDU from the upper layer.

[0063] In an embodiment, the RLC transmission controller (109) transmits the indication to the upper layer of the successful discard of the at least one RLC SDU associated with the SN when the at least one RLC SDU is successfully discarded. This ensures that the upper layer is informed about the status of the discarded data units, allowing it to take appropriate actions, such as adjusting the flow of data or initiating retransmissions if necessary.

[0064] In an embodiment, the RLC transmission controller (109) sets the Transmission-Next-Acknowledgement (TX_Next_Ack) parameter to the SN of the first RLC SDU for which a positive acknowledgment has not been received and a discard indication is not received from the upper layer. This mechanism ensures that the transmission controller keeps track of the sequence numbers of the data units that need to be acknowledged, thereby facilitating efficient management of the transmission window and reducing the likelihood of data loss or duplication.

[0065] In an embodiment, the RLC transmission controller (109) performs the re-association of the SN of the at least one RLC SDUs after discarding the at least one RLC SDU or a segment of the RLC SDU when the at least one pending RLC SDUs or a segment of RLC SDU is not transmitted to lower layers. Further, the RLC transmission controller (109) reassigns the SN of the at least one discarded RLC SDUs to the at least one RLC SDUs that are not indicated to be discarded from the upper layer. This re-association process helps optimize the utilization of sequence numbers and ensures that the transmission controller can manage the transmission of pending data units.

[0066] In an embodiment, the RLC transmission controller (109) skips prioritizing the at least one AMD PDU that contains previously transmitted RLC SDUs or RLC SDUs segments that are indicated for discard from the upper layer for transmissions over AMD PDUs that contain not previously transmitted RLC SDUs or RLC SDU segments. By doing so, the transmission controller prioritizes the transmission of new data units over retransmissions of data units that are likely to be discarded, thereby improving the overall efficiency and performance of the data transmission process.

[0067] In an embodiment, the RLC transmission controller (109) updates the Transmission-Next parameter (TX_Next) to increment by one when a segment of the RLC SDU that maps to the last byte of RLC SDU is discarded and is yet not contained in the UMD PDU and at least one other segment of the same RLC SDU is contained in the UMD PDU and has been submitted to the lower layer. This update ensures that the transmission controller accurately tracks the progress of data transmission and maintains the correct sequence of data units, thereby reducing the likelihood of data loss or duplication.

[0068] In an embodiment, the RLC transmission controller (109) determines whether the NACK for the at least one RLC SDU or the segment of RLC SDU is received from a receiving device. Further, the RLC transmission controller (109) retransmits the at least one RLC SDU or the segment of the RLC SDU for which the NACK is received if the SN of the corresponding RLC SDU falls within the range TX_Next_Ack <= SN <= the highest SN of the AMD PDU among the AMD PDUs submitted to the lower layer and if the discard indication is not received from the upper layer for the RLC SDU. This retransmission mechanism ensures that data units that have not been successfully received are retransmitted, thereby improving the reliability of the data transmission process.

[0069] In an embodiment, the RLC transmission controller (109) skips retransmission of the at least one RLC SDU for which the NACK is received when the discard indication is received for the at least one RLC SDU from the upper layer. Also, the RLC transmission controller (109) skips retransmission of the at least one RLC SDU for which the NACK is received. Also, the RLC transmission controller (109) skips incrementing the Retransmission count (RETX_COUNT) for the at least one corresponding RLC SDU. Also, the RLC transmission controller (109) skips considering the Retransmission count that is exceeding a preconfigured maximum retransmission threshold value. Also, the RLC transmission controller (109) skips indicating to the upper layer that the maximum retransmission has been reached for the at least one RLC SDU.

[0070] In an embodiment, the RLC transmission controller (109) updates the Transmission-Next-Acknowledgement (TX_Next_Ack) parameter based on the sequence number of the discarded RLC SDUs when the number of discarded RLC SDUs is greater than half of a transmission window. This update ensures that the transmission controller accurately tracks the progress of data transmission and maintains the correct sequence of data units, thereby reducing the likelihood of data loss or duplication.

[0071] In an embodiment, the upper layer is at least one of a Packet Data Convergence Protocol layer. The Packet Data Convergence Protocol layer is responsible for ensuring that data packets are correctly formatted and transmitted over the network, thereby improving the overall efficiency and performance of the data transmission process.

[0072] In an embodiment, the lower layer is at least one of a Medium Access Control layer. The Medium Access Control layer is responsible for managing access to the physical transmission medium, thereby ensuring that data packets are transmitted efficiently and reliably over the network. By coordinating with the upper and lower layers, the RLC transmission controller (109) helps improve the overall performance and reliability of the data transmission process.

[0073] Fig 2 is a flow diagram that illustrates a method for handling RLC transmission for XR in a communication network system according to embodiments disclosed herein.

[0074] At block 201, the method includes receiving the discard indication at the RLC layer from the upper layer to discard at least one RLC SDU associated with the SN. This discard indication is typically generated when the upper layer, such as the PDCP layer, determines that data packets are no longer needed. This could be due to various reasons such as the data becoming obsolete, the application no longer requiring the data, or network congestion necessitating the prioritization of other data packets. Upon receiving this indication, the RLC layer is informed that the specific RLC SDUs associated with the given SN is discarded.

[0075] At block 203, the method includes abandoning or stopping the transmission or retransmission of at least one RLC SDU segment of the RLC SDU and RLC data Protocol Data Unit (PDU) when the discard indication is received for the at least one corresponding RLC SDU from the upper layer. This step ensures that the network resources are not wasted on transmitting data that is no longer needed. By halting the transmission or retransmission processes, the method helps in reducing unnecessary network load and improving overall efficiency.

[0076] Furthermore, the method may include additional steps to manage the state of the RLC transmission buffers and update the status reports accordingly. For instance, the RLC layer may need to adjust its transmission window and update its status to reflect the discarded SDUs. This ensures that the RLC layer maintains an accurate representation of the data that needs to be transmitted or retransmitted, thereby preventing any inconsistencies or errors in the communication process. Further, the method may involve notifying the upper layers about the discard action, allowing them to take any necessary corrective measures or adjustments in their data handling strategies.

[0077] At block 205, the method includes performing re-association of the SN of the at least one RLC SDUs after discarding the at least one RLC SDU or a segment of the RLC SDU, when the at least one RLC SDUs or a segment of pending RLC SDU is not transmitted to lower layers

[0078] At block 207, the method includes reassigning the SN of the at least one discarded RLC SDUs to the at least one RLC SDUs that are not indicated to be discarded from the upper layer.

[0079] At block 209, the method includes determining whether a negative acknowledgement (NACK) for the at least one RLC SDU or the segment of RLC SDU is received from a receiving device.

[0080] At block 211, the method includes retransmitting the at least one RLC SDU or the segment of the RLC SDU for which the NACK is received, if the SN of the corresponding RLC SDU falls within the range TX_Next_Ack <= SN < = the highest SN of the AMD PDU among the AMD PDUs submitted to lower layer and if the discard indication is not received from the upper layer for the RLC SDU

[0081] In an embodiment, the method includes transmitting an indication to the upper layer of a successful discard of the at least one RLC SDU associated with the SN, when the at least one RLC SDU is successfully discarded.

[0082] In an embodiment, the method includes setting transmission-Next-Acknowledgement parameter to the SN of the first RLC SDU for which a positive acknowledgment has not been received and a discard indication is not received from the upper layer.

[0083] In an embodiment, the method includes skip prioritizing at least one AMD PDU that contains previously transmitted RLC SDUs or RLC SDUs segments that are indicated for discard for transmissions over AMD PDUs that contains not previously transmitted RLC SDUs or RLC SDU segments for discard.

[0084] In an embodiment, the method includes updating Transmission-Next parameter to increment by one, when a segment of the RLC SDU that maps to last byte of RLC SDU is discarded and is yet not contained in the UMD PDU and at least one other segment of the same RLC SDU is contained in the UMD PDU and has been submitted to lower layer.

[0085] In an embodiment, the method includes skip retransmission of the at least one RLC SDU for which the NACK is received, when the discard indication is received for the at least one RLC SDU from the upper layer.

[0086] In an embodiment, the method includes skip incrementing Retransmission count for the at least one corresponding RLC SDU, when the discard indication is received for the at least one RLC SDU from the upper layer.

[0087] In an embodiment, the method includes skip considering the Retransmission count that is exceeding a preconfigured maximum retransmission threshold value, when the discard indication is received for the at least one RLC SDU from the upper layer.

[0088] In an embodiment, the method includes skip indicating to the upper layer that the maximum retransmission has been reached for the at least one RLC SDU, when the discard indication is received for the at least one RLC SDU from the upper layer.

[0089] In an embodiment, the method includes updating the Transmission-Next-Acknowledgement parameter based on the sequence number of the discarded RLC SDUs, when the number of discarded RLC SDUs is greater than half of a transmission window.

[0090] Fig 3 is the flow diagram that illustrates the enhanced RLC transmit operation to handle acknowledgment at the transmitting side of AM RLC entity for XR according to embodiments disclosed herein. At block 301, the transmitting device (101) receives a positive acknowledgment for RLC SDU with SN=x. The transmitting device (101) can be an AM RLC entity. At block 303, the transmitting device (101) sends a notification to upper layers of the successful delivery of the RLC SDU upon receiving the positive acknowledgment. At block 305, the transmitting device (101) sets transmission-Next-Acknowledgement to SN of RLC SDU with the smallest SN whose SN falls within the range TX-Next-Ack<=SN<=TX-Next and for which a positive acknowledgment has not been received yet and for which discard indication is not received from the upper layer.

[0091] In an embodiment, the transmitting RLC entity of the transmitting device (101) (e.g., transmitting UM RLC entity or transmitting side of AM RLC entity) performs the RLC sequence number re-association after discarding the received RLC SDU(s) and / or RLC data PDU(s) as indicated for discard by the PDCP entity. The transmitting RLC entity reassigns the sequence number of one or more RLC SDU(s) or RLC data PDU(s) which are discarded to the immediately following RLC SDU(s) and / or RLC data PDU(s) that have not been indicated for the discard by the PDCP entity. This reassignment ensures that the sequence numbers remain contiguous and that there are no gaps in the sequence, which helps in maintaining the integrity and order of the data transmission.

[0092] In another embodiment, the transmitting RLC entity (e.g., transmitting UM RLC entity or transmitting side of AM RLC entity) performs the RLC sequence number re-association after discarding the received RLC SDU or a segment thereof as indicated for discard by the PDCP entity if neither the RLC SDU nor a segment thereof has been submitted to the lower layers. The transmitting RLC entity reassigns the sequence number of one or more RLC SDU(s) which are discarded to the immediately following RLC SDU(s) that have not been indicated for the discard by the PDCP entity. This process ensures that the sequence numbers are reassigned in a manner that maintains the order of transmission and acknowledgment, thereby preventing any potential confusion or errors in the data flow.

[0093] In an embodiment, when receiving a positive acknowledgment for an RLC SDU with SN = x, the transmitting side of an AM RLC entity sends an indication to the upper layers of successful delivery of the RLC SDU. Further, the transmitting side of an AM RLC entity sets TX_Next_Ack equal to the SN of the RLC SDU with the smallest SN whose SN falls within the range TX_Next_Ack <= SN <= TX_Next and for which a positive acknowledgment has not been received yet and for which discard indication is not received from PDCP. The TX_Next_Ack is a state variable that holds the value of the SN of the next RLC SDU for which a positive acknowledgment is to be received in-sequence. Also, it serves as the lower edge of the transmitting window (may also be referred to as the next to be acknowledged' sequence number). TX_Next is a state variable that holds the value of the SN to be assigned for the next newly generated AMD PDU (may also be referred to as the next to be transmitted' sequence number).

[0094] The process described ensures that the transmitting RLC entity efficiently manages the sequence numbers and acknowledgments. By reassigning sequence numbers and updating state variables such as TX_Next_Ack and TX_Next, the system can handle acknowledgments and retransmissions, reducing the likelihood of data loss or duplication.

[0095] In an embodiment, a few examples of proposed specification for the transmit operation of the RLC SDU discard handling are provided as follows:

[0096] Example 1 illustrates the procedure followed by the transmitting side of an AM RLC entity upon receiving a positive acknowledgment for an RLC SDU with SN = x.

[0097] -An indication of successful delivery of the RLC SDU is sent to the upper layers;

[0098] -set TX_Next_Ack equal to the SN of the RLC SDU with the smallest SN that falls within the range TX_Next_Ack <= SN <= TX_Next. This adjustment is made for RLC SDUs for which a positive acknowledgment has not yet been received and for which no discard indication has been received from the upper layer (e.g., PDCP).

[0099] Example 2 describes the actions taken by the transmitting side of an AM RLC entity upon receiving a positive acknowledgment for an RLC SDU with SN = x.

[0100] -The transmitting side shall send an indication to the upper layers of the successful delivery of the RLC SDU;

[0101] set TX_Next_Ack equal to the SN of the RLC SDU with the smallest SN that falls within the range TX_Next_Ack <= SN <= TX_Next, for which a positive acknowledgment has not yet been received, and which is not yet discarded based on an indication received from a higher layer (e.g., PDCP).

[0102] In an embodiment, when a large number of RLC SDUs are indicated to be discarded by the upper layer, the transmitting window of the RLC AM entity would shrink, and this may lead to window stalling or affect the RLC transmission (e.g., the transmitting side of an AM RLC entity cannot submit to the lower layer any AMD PDU whose SN falls outside of the transmitting window). Further, if more than half of the transmission window RLC SDUs are discarded, this may also lead to a Hyper Frame Number (HFN) un-synchronization issue. The transmission window is defined as a range of sequence numbers (SN) such that SN falls within the transmitting window if TX_Next_Ack <= SN < TX_Next_Ack + AM_Window_Size. To overcome this issue, the TX_Next_Ack of the transmitting side of an AM RLC entity is updated considering the sequence number of the discarded RLC SDUs. In an alternative embodiment, TX_Next_Ack of the transmitting side of an AM RLC entity is updated when the RLC entity sends RLC discard information to the receiving side of the peer AM RLC entity and receives an updated Status PDU (i.e., Acknowledgement) in response.

[0103] Fig 4 is a flow diagram that illustrates an enhanced RLC transmit operation to handle SDU discard at the transmitting side of AM RLC entity for XR according to embodiments disclosed herein. At block 401, the transmitting device (101) receives an indication for discard from the upper layer for RLC SDU with SN=x. At block 403, the transmitting device (101) sends an indication to the upper layers of successful discard of the RLC SDU upon receiving the discard indication. At block 405, the transmitting device (101) sets TX-Next-Ack equal to the SN of the RLC SDU with the smallest SN whose SN falls within the range TX-Next-Ack<=SN<=TX-Next and for which a positive acknowledgment has not been received yet and for which discard indication is not received from the upper layer.

[0104] In an embodiment, when receiving a discard indication for an RLC SDU with SN = x from the upper layers, the transmitting side of an AM RLC entity sends an indication to the upper layers of successful discard of the RLC SDU. Further, the transmitting side of an AM RLC entity sets TX_Next_Ack equal to the SN of the RLC SDU with the smallest SN whose SN falls within the range TX_Next_Ack <= SN <= TX_Next and for which a positive acknowledgment has not been received yet and for which discard indication is not received from PDCP. In an alternative embodiment, the step for sending an indication to the upper layers of successful discard of the RLC SDU may be omitted.

[0105] The enhanced RLC transmit operation described herein ensures efficient handling of SDU discard scenarios, which is used for maintaining the quality of service in XR applications. By promptly acknowledging the discard and adjusting the TX_Next_Ack parameter, the transmitting device can manage the transmission window and avoid unnecessary retransmissions. This mechanism helps in optimizing the use of network resources and reduces latency.

[0106] Further, the flexibility to omit the step of sending an indication to the upper layers of successful discard in certain embodiments provides additional optimization opportunities. In scenarios where the upper layers do not require explicit discard notifications, this omission can further streamline the transmit operation, reducing processing overhead and improving overall system performance. This adaptability makes the enhanced RLC transmit operation suitable for a wide range of deployment scenarios, catering to different network configurations and application requirements.

[0107] In an embodiment, a few examples of the proposed specification for the transmit operation of the RLC SDU discard handling are provided as follows:

[0108] In example 3, when an indication is received from the upper layer (e.g., PDCP) to discard an RLC SDU with SN = x, the transmitting side of an AM RLC entity shall:

[0109] -Send an indication to the upper layers of the successful discard of the RLC SDU;

[0110] -Set TX_Next_Ack equal to the SN of the RLC SDU with the smallest SN whose SN falls within the range TX_Next_Ack <= SN <= TX_Next and for which a discard indication from the upper layer is not received.

[0111] In example 4, upon receiving an indication from the upper layer (e.g., PDCP) to discard an RLC SDU with SN = x, the transmitting side of an AM RLC entity shall:

[0112] -Send an indication to the upper layers of the successful discard of the RLC SDU,

[0113] -Set TX_Next_Ack equal to the SN of the RLC SDU with the smallest SN whose SN falls within the range TX_Next_Ack <= SN <= TX_Next and for which a positive acknowledgment has not been received yet and which is not yet discarded based on the indication received from PDCP.

[0114] In an embodiment, the transmitting side of an Acknowledged Mode (AM) RLC entity may not prioritize transmission of AMD PDUs containing previously transmitted RLC SDUs or RLC SDU segments that are indicated for discard by the PDCP entity over transmission of AMD PDUs containing not previously transmitted RLC SDUs or RLC SDU segments.

[0115] Fig. 5 is a flow diagram that illustrates an enhanced RLC transmit operation to handle SDU discard at the transmitting UM RLC entity for XR, according to embodiments as disclosed herein.

[0116] At block 501, the transmitting device (101) receives an indication for discard from upper layer for an RLC SDU.

[0117] At block 503, the transmitting device (101) determines whether a segment that maps to last byte of an RLC SDU is discarded when indicated by PDCP entity and it is yet not contained in a UMD PDU while at least one other segment of same RLC SDU has been submitted in UMD PDU to lower layer.

[0118] At block 505, the transmitting device (101) increments TX-Next by one.

[0119] In an embodiment, if a segment that maps to the last byte of an RLC SDU is discarded when indicated by the PDCP entity and it is yet not contained in a UMD PDU while at least one other segment of same RLC SDU has been submitted in a UMD PDU to lower layer, the transmitting UM RLC entity increments TX_Next by one. This is illustrated in FIG. 3.

[0120] In example 5, when submitting a UMD PDU to lower layer, the transmitting UM RLC entity shall: if the UMD PDU contains a segment of an RLC SDU, set the SN of the UMD PDU to TX_Next;

[0121] if the UMD PDU contains a segment that maps to the last byte of an RLC SDU, then increment TX_Next by one.

[0122] The transmitting UM RLC entity shall

[0123] - if a segment that maps to the last byte of an RLC SDU is discarded when indicated by the PDCP entity and it is yet not contained in a UMD PDU while at least one other segment of same RLC SDU has been submitted in a UMD PDU to lower layer, then increment TX_Next by one.

[0124] In an embodiment, when receiving a negative acknowledgement for an RLC SDU or an RLC SDU segment by a STATUS PDU from its peer AM RLC entity, the transmitting side of the AM RLC entity considers the RLC SDU or the RLC SDU segment for which a negative acknowledgement was received for retransmission, if it is not indicated for discard by the PDCP layer and if the SN of the corresponding RLC SDU falls within the range TX_Next_Ack <= SN < = the highest SN of the AMD PDU among the AMD PDUs submitted to lower layer.

[0125] In example 6, when receiving a negative acknowledgement for an RLC SDU or an RLC SDU segment by a STATUS PDU from its peer AM RLC entity, the transmitting side of the AM RLC entity shall:

[0126] - if the SN of the corresponding RLC SDU falls within the range TX_Next_Ack <= SN < = the highest SN of the AMD PDU among the AMD PDUs submitted to lower layer and if it is not indicated for discard by the PDCP layer:

[0127] - consider the RLC SDU or the RLC SDU segment for which a negative acknowledgement was received for retransmission.

[0128] When an RLC SDU or an RLC SDU segment is considered for retransmission, the transmitting side of the AM RLC entity shall:

[0129] - if the RLC SDU or RLC SDU segment is considered for retransmission for the first time:

[0130] - set the RETX_COUNT associated with the RLC SDU to zero.

[0131] - else, if it (the RLC SDU or the RLC SDU segment that is considered for retransmission) is not pending for retransmission already and the RETX_COUNT associated with the RLC SDU has not been incremented due to another negative acknowledgment in the same STATUS PDU:

[0132] - increment the RETX_COUNT.

[0133] - if RETX_COUNT = maxRetxThreshold:

[0134] - indicate to upper layers that max retransmission has been reached.

[0135] In an embodiment, the transmitting RLC entity skips retransmission for a RLC SDU which has been negatively acknowledged and skips incrementing RETX_COUNT for the RLC SDU when the RLC SDU is indicated by PDCP entity for discard.

[0136] In an embodiment, the transmitting side of the AM RLC entity (UE or network) skips retransmission for an RLC SDU which has been negatively acknowledged and skips incrementing RETX_COUNT for the RLC SDU when the RLC SDU is indicated in the RLC discard signaling to the peer (network or UE) receiving side AM RLC entity. This approach helps in optimizing the retransmission process by avoiding unnecessary retransmissions of data that are no longer required, thereby saving valuable network resources and improving overall transmission efficiency. By not incrementing the RETX_COUNT, the system can prevent the unnecessary triggering of retransmission thresholds, which can lead to more efficient use of the available bandwidth.

[0137] In another embodiment, the transmitting side of the AM RLC entity skips considering the RETX_COUNT exceeding the maximum retransmission threshold value configured and skips indicating the upper layer that the maximum retransmission has been reached for the RLC SDU (e.g., indicating a Radio Link Failure) when the RLC SDU is indicated by the PDCP entity for discard. This embodiment ensures that the upper layers are not prematurely informed of a link failure due to retransmission limits being reached, which could otherwise lead to unnecessary protocol overhead and potential disruptions in the communication session. By aligning the discard indications from the PDCP entity with the retransmission logic of the RLC entity, the system can achieve a more coherent and efficient handling of data discards.

[0138] In yet another embodiment, the transmitting side of the AM RLC entity abandons the retransmission of the RLC SDUs and / or RLC Data PDUs (e.g., containing the RLC SDU or a segment of the RLC SDU) when the RLC SDU is indicated for discard by the upper layer. This abandonment of retransmission ensures that the system does not waste resources on data that the upper layers have already deemed unnecessary. It also helps in maintaining the integrity and timeliness of the data that is still considered relevant, thereby improving the overall quality of service.

[0139] Furthermore, in an embodiment, the transmitting UM RLC entity and / or transmitting side of the AM RLC entity abandons the transmission of the RLC SDUs and / or SDU segments and / or RLC Data PDUs (e.g., containing the RLC SDU or a segment of the RLC SDU) when the RLC SDU is indicated for discard by the upper layer. This is useful in scenarios where the upper layers have dynamically determined that certain data is no longer needed, allowing the RLC entities to promptly cease the transmission of such data. This conserves network resources and reduces the potential for congestion and delays within the network.

[0140] FIG. 6 illustrates is a structure of a user equipment according to embodiments of the disclosure.

[0141] As shown in FIG. 6, the UE according to an embodiment may include a transceiver 610, a memory 620, and a processor 630. The transceiver 610, the memory 620, and the processor 630 of the UE may operate according to a communication method of the UE described above. However, the components of the UE are not limited thereto. For example, the UE may include more or fewer components than those described above. In addition, the processor 630, the transceiver 610, and the memory 620 may be implemented as a single chip. Also, the processor 630 may include at least one processor. Furthermore, the UE of FIG. 6 corresponds to a UE, a transmitting device or a receiving device according to embodiments of the disclosure.

[0142] The transceiver 610 collectively refers to a UE receiver and a UE transmitter, and may transmit / receive a signal to / from a base station or a network entity. The signal transmitted or received to or from the base station or a network entity may include control information and data. The transceiver 610 may include a RF transmitter for up-converting and amplifying a frequency of a transmitted signal, and a RF receiver for amplifying low-noise and down-converting a frequency of a received signal. However, this is only an example of the transceiver 610 and components of the transceiver 610 are not limited to the RF transmitter and the RF receiver.

[0143] Also, the transceiver 610 may receive and output, to the processor 630, a signal through a wireless channel, and transmit a signal output from the processor 630 through the wireless channel.

[0144] The memory 620 may store a program and data required for operations of the UE. Also, the memory 620 may store control information or data included in a signal obtained by the UE. The memory 620 may be a storage medium, such as read-only memory (ROM), random access memory (RAM), a hard disk, a CD-ROM, and a DVD, or a combination of storage media.

[0145] The processor 630 may control a series of processes such that the UE operates as described above. For example, the transceiver 610 may receive a data signal including a control signal transmitted by the base station or the network entity, and the processor 630 may determine a result of receiving the control signal and the data signal transmitted by the base station or the network entity.

[0146] FIG. 7 illustrates is a structure of a network entity according to embodiments of the disclosure.

[0147] As shown in FIG. 7, the network entity according to an embodiment may include a transceiver 710, a memory 720, and a processor 730. The transceiver 710, the memory 720, and the processor 730 of the network entity may operate according to a communication method of the network entity described above. However, the components of the network entity are not limited thereto. For example, the network entity may include more or fewer components than those described above. In addition, the processor 730, the transceiver 710, and the memory 720 may be implemented as a single chip. Also, the processor 730 may include at least one processor. Furthermore, the network entity of FIG. 7 corresponds to a network entity, a transmitting device or a receiving device according to embodiments of the disclosure.

[0148] The transceiver 710 collectively refers to a network entity receiver and a network entity transmitter, and may transmit / receive a signal to / from a terminal (UE) or a network entity. The signal transmitted or received to or from the terminal or a network entity may include control information and data. The transceiver 710 may include a RF transmitter for up-converting and amplifying a frequency of a transmitted signal, and a RF receiver for amplifying low-noise and down-converting a frequency of a received signal. However, this is only an example of the transceiver 710 and components of the transceiver 710 are not limited to the RF transmitter and the RF receiver.

[0149] Also, the transceiver 710 may receive and output, to the processor 730, a signal through a wireless channel, and transmit a signal output from the processor 730 through the wireless channel.

[0150] The memory 720 may store a program and data required for operations of the network entity. Also, the memory 720 may store control information or data included in a signal obtained by the network entity. The memory 720 may be a storage medium, such as read-only memory (ROM), random access memory (RAM), a hard disk, a CD-ROM, and a DVD, or a combination of storage media.

[0151] The processor 730 may control a series of processes such that the network entity operates as described above. For example, the transceiver 710 may receive a data signal including a control signal transmitted by the terminal, and the processor 730 may determine a result of receiving the control signal and the data signal transmitted by the terminal.

[0152] The foregoing description of the specific embodiments will fully reveal the general nature of the embodiments herein such that others can readily modify and / or adapt such specific embodiments for various applications without departing from the generic concept. Therefore, such adaptations and modifications are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Thus, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modifications within the scope of the embodiments as described herein.

Claims

1.A method performed by a transmitting device in a wireless communication system, the method comprising:receiving, by a radio link control (RLC) entity of the transmitting device, a first discard indication for a first RLC service data unit (SDU) from a packet data convergence protocol (PDCP) entity of the transmitting device; andstopping, by the RLC entity, a transmission or a retransmission of the first RLC SDU or a segment of the first RLC SDU.2.The method of claim 1, further comprising:transmitting, by the RLC entity, a successful discard indication for the first RLC SDU to the PDCP entity.3.The method of claim 1, further comprising:performing, by the RLC entity, sequence number re-association after discarding the first RLC SDU.4.The method of claim 1, further comprising:updating, by the RLC entity which is configured with an acknowledged mode (AM), transmission-next-acknowledgement (TX_NEXT_ACK) state variable based on a sequence number of the first RLC SDU.5.The method of claim 1, further comprising:updating, by the RLC entity which is configured with an unacknowledged mode (UM), transmission-next (TX_NEXT) state variable based on a sequence number of the first RLC SDU.6.The method of claim 1, further comprising:receiving, by the RLC entity, a negative acknowledgement for a second RLC SDU that is previously transmitted to a receiving device; andin case that a second discard indication for the second RLC SDU is received from the PDCP entity, skipping a retransmission of the second RLC SDU.7.The method of claim 6, wherein a retransmission count (RETX_COUNT) state variable for the second RLC SDU is not incremented.8.The method of claim 1, wherein, in case that the first RLC PDU is previously transmitted to a receiving device, a transmission of the first RLC SDU is not prioritized over a transmission of a third RLC SDU that is not previously transmitted.9.A transmitting device in a wireless communication system, the transmitting device comprising:a transceiver; anda controller coupled with the transceiver and configured to:receive, by a radio link control (RLC) entity of the transmitting device, a first discard indication for a first RLC service data unit (SDU) from a packet data convergence protocol (PDCP) entity of the transmitting device; andstop, by the RLC entity, a transmission or a retransmission of the first RLC SDU or a segment of the first RLC SDU.10.The transmitting device of claim 9, wherein the controller is further configured to:transmit, by the RLC entity, a successful discard indication for the first RLC SDU to the PDCP entity.11.The transmitting device of claim 9, wherein the controller is further configured to:perform, by the RLC entity, sequence number re-association after discarding the first RLC SDU.12.The transmitting device of claim 9, wherein the controller is further configured to:update, by the RLC entity which is configured with an acknowledged mode (AM), transmission-next-acknowledgement (TX_NEXT_ACK) state variable, based on a sequence number of the first RLC SDU.13.The transmitting device of claim 9, wherein the controller is further configured to:update, by the RLC entity which is configured with an unacknowledged mode (UM), transmission-next (TX_NEXT) state variable based on a sequence number of the first RLC SDU.14.The transmitting device of claim 9, wherein the controller is further configured to:receive, by the RLC entity, a negative acknowledgement for a second RLC SDU that is previously transmitted to a receiving device; andin case that a second discard indication for the second RLC SDU is received from the PDCP entity, skip a retransmission of the second RLC SDU,wherein a retransmission count (RETX_COUNT) state variable for the second RLC SDU is not incremented.15.The transmitting device of claim 9, wherein, in case that the first RLC PDU is previously transmitted to a receiving device, a transmission of the first RLC SDU is not prioritized over a transmission of a third RLC SDU that is not previously transmitted.

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