PDU drop indication in layer 2 process

Abstract

A method of wireless communication at a first wireless device is disclosed. The method includes transmitting, with the second wireless device, a plurality of PDUs associated with the DRB. The method includes detecting that at least one PDU of a plurality of PDUs associated with the DRB satisfies at least one drop criterion. The method includes transmitting, for the second wireless device, a drop status report associated with the at least one PDU satisfying the at least one drop criterion.

Description

Technical Field

[0001] The present disclosure relates generally to communication systems and, more particularly, to protocol data unit (PDU) discarding. Background Art

[0002] Wireless communication systems are widely deployed to provide a variety of telecommunication services, such as telephony, video, data, messaging, and broadcast. Typical wireless communication systems may employ multiple access technologies that can support communication with multiple users by sharing available system resources. Examples of such multiple access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

[0003] These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate at city, country, region, and even global levels. An example of a telecommunication standard is 5G New Radio (NR). 5G NR is part of the continuous mobile broadband evolution promulgated by the Third Generation Partnership Project (3GPP) to meet new requirements associated with latency, reliability, security, scalability (e.g., with the Internet of Things (IoT)) and other requirements. 5G NR includes services associated with enhanced mobile broadband (eMBB), massive machine type communication (mMTC), and ultra-reliable low latency communication (URLLC). Certain aspects of 5G NR may be based on 4G Long Term Evolution (LTE) standards. It is necessary to further improve 5G NR technology. In addition, these improvements may also be applicable to other multiple access technologies and telecommunication standards that employ these technologies. Summary of the invention

[0004] A simplified summary of one or more aspects is provided below to provide a basic understanding of these aspects. This overview is not an extensive overview of all expected aspects. This overview neither identifies the key or important elements of all aspects, nor describes the scope of any or all aspects. Its sole purpose is to provide some concepts of one or more aspects in a simplified form as a prelude to a more detailed description provided later.

[0005] In one aspect of the present disclosure, a method, computer-readable medium, and apparatus for wireless communication at a first wireless device are provided. The apparatus includes a memory and at least one processor coupled to the memory, and based at least in part on information stored in the memory, the at least one processor is configured to: transmit a plurality of protocol data units (PDUs) associated with a data radio bearer (DRB) to a second wireless device; detect that at least one of the plurality of PDUs associated with the DRB satisfies at least one discard criterion; and send a discard status report associated with the at least one PDU that satisfies the at least one discard criterion to the second wireless device.

[0006] In one aspect of the present disclosure, a method, computer-readable medium, and apparatus for wireless communication at a second wireless device are provided. The apparatus includes a memory and at least one processor coupled to the memory, and based at least in part on information stored in the memory, the at least one processor is configured to: transmit a plurality of protocol data units (PDUs) associated with a data radio bearer (DRB) to a first wireless device; receive a discard status report associated with at least one PDU in the plurality of PDUs that satisfies at least one discard criterion from the first wireless device; and update a sliding window of the DRB based on the discard status report.

[0007] In one aspect of the present disclosure, a method, computer-readable medium, and apparatus for wireless communication at a first wireless device are provided. The apparatus includes a memory and at least one processor coupled to the memory, and based at least in part on information stored in the memory, the at least one processor is configured to: transmit a plurality of protocol data units (PDUs) associated with a data radio bearer (DRB) with a second wireless device; receive an indication of a sequence number gap associated with at least one PDU in the plurality of PDUs from the second wireless device based on expiration of a packet data convergence protocol (PDCP) discard timer; and update a sliding window of the DRB based on the sequence number gap.

[0008] In one aspect of the present disclosure, a method, computer-readable medium, and apparatus for wireless communication at a second wireless device are provided. The apparatus includes a memory and at least one processor coupled to the memory, and based at least in part on information stored in the memory, the at least one processor is configured to: transmit a plurality of protocol data units (PDUs) associated with a data radio bearer (DRB) with a first wireless device; detect expiration of a packet data convergence protocol (PDCP) discard timer associated with at least one of the plurality of PDUs; and send an indication of a sequence number gap associated with the at least one of the plurality of PDUs to the first wireless device based on the expiration of the PDCP discard timer.

[0009] To achieve the foregoing and related purposes, one or more aspects include the features fully described below and particularly pointed out in the claims. The following description and the accompanying drawings set forth in detail certain illustrative features of the one or more aspects. However, these features are only indicative of only some of the various ways in which the principles of the various aspects can be employed. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a diagram illustrating an example of a wireless communication system and an access network.

[0011] Figure 2A is a diagram showing an example of a first frame according to various aspects of the present disclosure.

[0012] Figure 2B is a schematic diagram illustrating an example of downlink (DL) channels within a subframe according to various aspects of the present disclosure.

[0013] Figure 2C is a diagram illustrating an example of a second frame according to various aspects of the present disclosure.

[0014] Figure 2D is a diagram illustrating an example of uplink (UL) channels within a subframe according to various aspects of the present disclosure.

[0015] Figure 3 is a diagram showing an example of a base station and a user equipment (UE) in an access network.

[0016] Figure 4 is a diagram illustrating an example of an extended reality (XR) service.

[0017] Figure 5 is a diagram showing an example of generating a radio link control (RLC) protocol data unit (PDU) from an RLC service data unit (SDU).

[0018] Figure 6 is a diagram showing an example in which an RLC transmitter discards a PDU.

[0019] Figure 7 is a diagram showing an example in which an RLC receiver discards a PDU.

[0020] Figure 8 is an example discard status report.

[0021] Fig. 9 is an example discard status report.

[0022] Fig.10 is an example discard status report.

[0023] Fig.11 is an example discard status report.

[0024] Fig.12 is a diagram illustrating an example discard indication control PDU.

[0025] Fig.13 is a diagram illustrating an example discard indication control PDU.

[0026] Fig.14 is a diagram illustrating example communications between an RLC receiver and an RLC transmitter.

[0027] Fig.15 is a flow chart illustration of a method of wireless communication.

[0028] Fig.16 is a flow chart illustration of a method of wireless communication.

[0029] Fig.17 is a flow chart illustration of a method of wireless communication.

[0030] Fig.18 is a flow chart illustration of a method of wireless communication.

[0031] Fig.19 is a flow chart illustration of a method of wireless communication.

[0032] Fig. 20 is a flow chart illustration of a method of wireless communication.

[0033] Fig.21 is a flow chart illustration of a method of wireless communication.

[0034] Fig. 22 is a flow chart illustration of a method of wireless communication.

[0035] Fig.23 are diagrams illustrating examples of hardware implementations for example apparatuses and / or network entities.

[0036] Fig.24is a diagram illustrating an example of a hardware implementation for an example network entity. DETAILED DESCRIPTION

[0037] In a layer 2 (L2) process, various types of events may trigger PDU discarding. For example, if a PDU misses a configured delay budget or a signaled delivery deadline, the PDU may become obsolete. If an RLC receiver discards a PDU but does not notify the RLC transmitter of the discard, the RLC transmitter may not advance a transmitter-side automatic repeat request (ARQ) window. This may delay further transmissions by the RLC transmitter. If an RLC transmitter discards a PDU but does not notify the RLC receiver of the discard, there may be a gap in the RLC PDU sequence number (SN). This may delay the advancement of the receiver-side ARQ window. Various techniques related to PDU discarding are described herein. In an example, a first wireless device transmits a plurality of PDUs associated with a DRB with a second wireless device. The first wireless device detects that at least one of the plurality of PDUs associated with the DRB satisfies at least one discard criterion. The first wireless device sends a discard status report associated with at least one PDU that satisfies at least one discard criterion to the second wireless device. The second wireless device may update a sliding window based on the discard status report. Thus, the discard status report can prevent the transmission of the second wireless device from being stalled, and thus can result in increased communication reliability at the first wireless device. In another example, the first wireless device transmits a plurality of PDUs associated with the DRB with the second wireless device. The first wireless device receives an indication of a sequence number gap associated with at least one of the plurality of PDUs from the second wireless device based on expiration of a PDCP discard timer. The first wireless device can update a sliding window of the DRB based on the sequence number gap. Thus, the indication of the sequence number gap can help the first wireless device update the sliding window, and can result in increased communication reliability at the first wireless device.

[0038] The detailed description set forth below in conjunction with the accompanying drawings describes various configurations and does not represent the only configuration in which the concepts described herein may be practiced. In order to provide a thorough understanding of the various concepts, the detailed description includes specific details. However, these concepts may be practiced without these specific details. In some cases, well-known structures and components are shown in block diagram form to avoid obscuring these concepts.

[0039] Several aspects of telecommunication systems are presented with reference to various apparatus and methods. These apparatus and methods are described in the detailed description below and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc. (collectively referred to as "elements"). Such elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether these elements are implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system.

[0040] For example, an element, or any part of an element, or any combination of elements can be implemented as a "processing system", which includes one or more processors. Examples of processors include microprocessors, microcontrollers, graphics processing units (GPUs), central processing units (CPUs), application processors, digital signal processors (DSPs), reduced instruction set computing (RISC) processors, systems on chip (SoCs), baseband processors, field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gate logic, discrete hardware circuits, and other suitable hardware configured to perform various functions described throughout the present disclosure. One or more processors in a processing system can execute software. Whether referring to software, firmware, middleware, microcode, hardware description language or other, software should be broadly interpreted as instructions, instruction sets, codes, code segments, program codes, programs, subroutines, software components, applications, software applications, software packages, routines, subroutines, objects, executable programs, threads of execution, programs, functions, or any combination thereof.

[0041] Therefore, in one or more example aspects, implementations and / or use cases, the described functions may be implemented in hardware, software or any combination thereof. If implemented in software, the functions may be stored or encoded as one or more instructions or codes on a computer-readable medium. Computer-readable media include computer storage media. Storage media may be any available medium that can be accessed by a computer. By way of example, such computer-readable media may include random access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), optical disk storage, magnetic disk storage, other magnetic storage devices, a combination of the aforementioned computer-readable media types, or any other medium that can be used to store computer executable code that can be accessed by a computer in the form of instructions or data structures.

[0042] Although various aspects, implementations and / or use cases are described in this application by illustrating some examples, additional or different aspects, implementations and / or use cases may appear in many different arrangements and scenarios. The various aspects, implementations and / or use cases described herein can be implemented across many different platform types, devices, systems, shapes, sizes, and packaging arrangements. For example, various aspects, implementations and / or use cases can be generated via integrated chip implementations and other devices based on non-module components (e.g., end-user devices, vehicles, communication devices, computing devices, industrial equipment, retail / purchase equipment, medical equipment, artificial intelligence (AI) enabled devices, etc.). Although some examples may or may not specifically point to use cases or applications, the applicability of various types of the described examples may appear. Various aspects, implementations and / or use cases can be from chip-level or modular components of one or more technologies incorporated herein to non-modular, non-chip-level implementations, and further to the range of aggregated, distributed or original equipment manufacturer (OEM) devices or systems. In some actual settings, the device incorporating the described aspects and features may also include additional components and features for the implementations and practices of the claimed and described aspects. For example, the transmission and reception of wireless signals necessarily include multiple components for analog and digital purposes (e.g., hardware components including antennas, RF chains, power amplifiers, modulators, buffers, processors, interleavers, adders / accumulators, etc.). The techniques described herein can be practiced in various devices of different sizes, shapes, and configurations, chip-level components, systems, distributed arrangements, aggregated or disaggregated components, end-user devices, etc.

[0043] The deployment of a communication system, such as a 5G New Radio (NR) system, can be arranged in a variety of ways in various components or constituent parts. In a 5G NR system or network, a network node, a network entity, a mobile element of a network, a radio access network (RAN) node, a core network node, a network element, or a network device, such as a base station (BS) or one or more units (or one or more components) performing base station functions, can be implemented in an aggregated or decomposed architecture. For example, a BS, such as a Node B (NB), an evolved NB (eNB), an NR BS (e.g., a gNB), a 5G NB, an access point (AP), a transmit receive point (TRP), or a cell, etc., can be implemented as an aggregated base station (also referred to as a standalone BS or a monolithic BS) or a decomposed base station.

[0044] The aggregated base station can be configured to utilize a radio protocol stack physically or logically integrated within a single RAN node. The decomposed base station can be configured to utilize a protocol stack physically or logically distributed between two or more units, such as one or more central or centralized units (CUs), one or more distributed units (DUs), or one or more radio units (RUs). In some aspects, the CU can be implemented within a RAN node, and one or more DUs can be co-located with the CU, or alternatively, can be geographically or virtually distributed in one or more other RAN nodes. The DU can be implemented to communicate with one or more RUs. Each of the CU, DU, and RU can be implemented as a virtual unit (i.e., a virtual central unit (VCU), a virtual distributed unit (VDU), or a virtual radio unit (VRU)).

[0045] Base station operation or network design may take into account the aggregated nature of base station functionality. For example, a disaggregated base station may be used in an integrated access backhaul (IAB) network, an open radio access network (O-RAN (network configuration such as the O-RAN Alliance Initiative) or a virtualized radio access network (vRAN, also known as a cloud radio access network (C-RAN)). Decomposition may include distributing functionality across two or more units at various physical locations, as well as virtually distributing functionality for at least one unit, which may enable flexibility in network design. Individual units of a disaggregated base station or disaggregated RAN architecture may be configured for wired or wireless communication with at least one other unit.

[0046] Figure 1 100 is a diagram illustrating an example of a wireless communication system and an access network. The wireless communication system shown includes a decomposed base station architecture. The decomposed base station architecture may include one or more CUs 110, which may communicate directly with a core network 120 via a backhaul link, or indirectly with a core network 120 through one or more decomposed base station units (such as a near real-time (near RT) RAN intelligent controller (RIC) 125 via an E2 link, or a non-real-time (non-RT) RIC 115 associated with a service management and orchestration (SMO) framework 105, or both). The CU 110 may communicate with one or more DUs 130 via corresponding mid-haul links such as an F1 interface. The DU 130 may communicate with one or more RUs 140 via corresponding fronthaul links. The RU 140 may communicate with corresponding UEs 104 via one or more radio frequency (RF) access links. In some implementations, a UE 104 may be served by multiple RUs 140 at the same time.

[0047] Each of the units (i.e., CU 110, DU 130, RU 140) and the near-RT RIC 125, the non-RT RIC 115, and the SMO framework 105 may include or be coupled to one or more interfaces configured to receive or send signals, data, or information (collectively referred to as signals) via a wired or wireless transmission medium. Each unit in the unit or an associated processor or controller that provides instructions to the communication interface of the unit may be configured to communicate with one or more of the other units via a transmission medium. For example, a unit may include a wired interface configured to receive a signal on a wired transmission medium or to send a signal to one or more other units in the other units. In addition, a unit may include a wireless interface, which may include a receiver, a transmitter, or a transceiver (such as a radio frequency (RF) transceiver) configured to receive a signal on a wireless transmission medium or to send a signal to one or more other units in the other units, or both.

[0048] In some aspects, CU 110 may host one or more higher layer control functions. Such control functions may include radio resource control (RRC), packet data convergence protocol (PDCP), service data adaptation protocol (SDAP), etc. Each control function may be implemented using an interface configured to transmit signals with other control functions hosted by CU 110. CU110 may be configured to process user plane functions (i.e., central unit-user plane (CU-UP)), control plane functions (i.e., central unit-control plane (CU-CP)), or a combination thereof. In some implementations, CU 110 may be logically split into one or more CU-UP units and one or more CU-CP units. The CU-UP unit may communicate bidirectionally with the CU-CP unit via an interface (e.g., via an E1 interface when implemented in an O-RAN configuration). If necessary, CU 110 may be implemented to communicate with DU 130 for network control and signaling.

[0049] DU 130 may correspond to a logical unit that includes one or more base station functions to control the operation of one or more RU 140. In some aspects, DU 130 may host one or more of a radio link control (RLC) layer, a medium access control (MAC) layer, and one or more high physical (PHY) layers (such as modules for forward error correction (FEC) encoding and decoding, scrambling, modulation, demodulation, etc.) at least in part according to a functional split (such as a functional split defined by 3GPP). In some aspects, DU 130 may also host one or more low PHY layers. Each layer (or module) may be implemented using an interface configured to transmit signals with other layers (and modules) hosted by DU 130 or control functions hosted by CU 110.

[0050] The lower layer functions may be implemented by one or more RUs 140. In some deployments, based at least in part on a functional split (such as a lower layer functional split), a RU 140 controlled by a DU 130 may correspond to a logical node that hosts RF processing functions or low PHY layer functions (e.g., performing fast Fourier transform (FFT), inverse FFT (iFFT), digital beamforming, physical random access channel (PRACH) extraction and filtering, etc.), or both. In such an architecture, the RU 140 may be implemented to handle over-the-air (OTA) communications with one or more UEs 104. In some implementations, real-time and non-real-time aspects of control and user plane communications with the RU 140 may be controlled by the corresponding DU 130. In some scenarios, this configuration may enable the DU 130 and the CU 110 to be implemented in a cloud-based RAN architecture (such as a vRAN architecture).

[0051] The SMO framework 105 may be configured to support RAN deployment and provisioning of non-virtualized and virtualized network elements. For non-virtualized network elements, the SMO framework 105 may be configured to support the deployment of dedicated physical resources for RAN coverage requirements, which may be managed via an operation and maintenance interface (such as an O1 interface). For virtualized network elements, the SMO framework 105 may be configured to interact with a cloud computing platform (such as an open cloud (O-cloud) 190) to perform network element lifecycle management (e.g., to instantiate virtualized network elements) via a cloud computing platform interface (such as an O2 interface). Such virtualized network elements may include, but are not limited to, CU 110, DU 130, RU 140, and near-RT RIC 125. In some implementations, the SMO framework 105 may communicate with hardware aspects of the 4G RAN (such as an open eNB (O-eNB) 111) via the O1 interface. In addition, in some implementations, the SMO framework 105 may communicate directly with one or more RUs 140 via the O1 interface. The SMO framework 105 may also include a non-RT RIC 115 configured to support the functionality of the SMO framework 105 .

[0052] The non-RT RIC 115 may be configured to include logic functions that implement non-real-time control and optimization of RAN elements and resources, artificial intelligence (AI) / machine learning (ML) (AI / ML) workflows (including model training and updating), or policy-based guidance of applications / features in the near-RT RIC 125. The non-RT RIC 115 may be coupled to or in communication with the near-RT RIC 125 (e.g., via an A1 interface). The near-RT RIC 125 may be configured to include logic functions that implement near-real-time control and optimization of RAN elements and resources via data collection and actions on an interface connecting one or more CUs 110, one or more DUs 130, or both, and O-eNBs with the near-RT RIC 125 (e.g., via an E2 interface).

[0053] In some implementations, in order to generate an AI / ML model to be deployed in the near-RT RIC 125, the non-RT RIC 115 may receive parameters or external enrichment information from an external server. Such information may be utilized by the near-RT RIC 125 and may be received from a non-network data source or network function at the SMO framework 105 or the non-RT RIC 115. In some examples, the non-RT RIC 115 or the near-RT RIC 125 may be configured to tune RAN behavior or performance. For example, the non-RT RIC 115 may monitor long-term trends and patterns of performance and employ AI / ML models to perform corrective actions through the SMO framework 105 (e.g., via reconfiguration of O1) or via the creation of a RAN management policy (such as an A1 policy).

[0054] At least one of the CU 110, the DU 130, and the RU 140 may be referred to as a base station 102. Therefore, the base station 102 may include one or more of the CU 110, the DU 130, and the RU 140 (each component indicated by a dotted line indicates that each component may be included in the base station 102 or may not be included in the base station 102). The base station 102 provides an access point to the core network 120 for the UE 104. The base station 102 may include a macro cell (a high-power cellular base station) and / or a small cell (a low-power cellular base station). Small cells include femto cells, pico cells, and micro cells. A network including small cells and macro cells may be referred to as a heterogeneous network. A heterogeneous network may also include a home evolved Node B (eNB) (HeNB), which may provide services to a restricted group called a closed subscriber group (CSG). The communication link between RU 140 and UE 104 may include an uplink (UL) (also referred to as a reverse link) transmission from UE 104 to RU140 and / or a downlink (DL) (also referred to as a forward link) transmission from RU 140 to UE 104. The communication link may use multiple-input multiple-output (MIMO) antenna technology, including spatial multiplexing, beamforming and / or transmit diversity. The communication link may pass through one or more carriers. Base station 102 / UE 104 may use a spectrum of up to Y megahertz (MHz) (e.g., 5, 10, 15, 20, 100, 400, etc. MHz) bandwidth per carrier allocated in a carrier aggregation of up to Yx MHz (x component carriers) for transmission in each direction. The carriers may or may not be adjacent to each other. The allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or fewer carriers may be allocated for DL ​​compared to UL). Component carriers may include a primary component carrier and one or more secondary component carriers. The primary component carrier may be referred to as a primary cell (PCell) and the secondary component carrier may be referred to as a secondary cell (SCell).

[0055] Certain UEs 104 may communicate with each other using a device-to-device (D2D) communication link 158. The D2D communication link 158 may use DL / UL wireless wide area network (WWAN) spectrum. The D2D communication link 158 may use one or more sidelink channels, such as a physical sidelink broadcast channel (PSBCH), a physical sidelink discovery channel (PSDCH), a physical sidelink shared channel (PSSCH), and a physical sidelink control channel (PSCCH). The D2D communication may be through a variety of wireless D2D communication systems, such as, for example, Bluetooth, Wi-Fi based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, LTE, or NR.

[0056] The wireless communication system may also include a Wi-Fi AP 150 that communicates with a UE 104 (also referred to as a Wi-Fi station (STA)) via a communication link 154, e.g., in a 5 GHz unlicensed spectrum, etc. When communicating in an unlicensed spectrum, the UE 104 / AP 150 may perform a clear channel assessment (CCA) prior to communication to determine whether a channel is available.

[0057] The electromagnetic spectrum is typically subdivided into various categories, bands, channels, etc. based on frequency / wavelength. In 5G NR, two initial operating bands have been identified with the frequency range names FR1 (410 MHz-7.125 GHz) and FR2 (24.25 GHz-52.6 GHz). Although a portion of FR1 is greater than 6 GHz, FR1 is often referred to (interchangeably) as the "sub-6 GHz" band in various documents and articles. A similar naming issue sometimes occurs with respect to FR2, which is often (interchangeably) referred to as the "millimeter wave" band in documents and articles, although it is different from the extremely high frequency (EHF) band (30 GHz-300 GHz) which is identified as the "millimeter wave" band by the International Telecommunication Union (ITU).

[0058] Frequencies between FR1 and FR2 are generally referred to as mid-band frequencies. Recent 5G NR research has identified the operating bands for these mid-band frequencies as the frequency range designation FR3 (7.125 GHz–24.25 GHz). The frequency bands falling within FR3 can inherit FR1 characteristics and / or FR2 characteristics, so the features of FR1 and / or FR2 can be effectively extended to mid-band frequencies. In addition, higher frequency bands are currently being explored to extend 5G NR operations beyond 52.6 GHz. For example, three higher operating bands have been identified as frequency range designations FR2-2 (52.6 GHz–71 GHz), FR4 (71 GHz–114.25 GHz), and FR5 (114.25 GHz–300 GHz). Each of these higher frequency bands falls within the EHF band.

[0059] In view of the above, unless otherwise specified, if the term "sub-6 GHz" or the like is used in this document, it may broadly refer to frequencies that may be less than 6 GHz, may be within FR1, or may include mid-band frequencies. In addition, unless otherwise specified, if the term "millimeter wave" or the like is used in this document, it may broadly refer to frequencies that may include mid-band frequencies, may be within FR2, FR4, FR2-2, and / or FR5, or may be within the EHF band.

[0060] The base station 102 and the UE 104 may each include multiple antennas (such as antenna elements, antenna panels, and / or antenna arrays) to facilitate beamforming. The base station 102 may transmit a beamformed signal 182 to the UE 104 in one or more transmit directions. The UE 104 may receive the beamformed signal from the base station 102 in one or more receive directions. The UE 104 may also transmit a beamformed signal 184 to the base station 102 in one or more transmit directions. The base station 102 may receive the beamformed signal from the UE 104 in one or more receive directions. The base station 102 / UE 104 may perform beam training to determine the best receive direction and transmit direction for each of the base station 102 / UE 104. The transmit and receive directions of the base station 102 may be the same or different. The transmit and receive directions of the UE 104 may be the same or different.

[0061] The base station 102 may include and / or be referred to as a gNB, a Node B, an eNB, an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), a transmit receive point (TRP), a network node, a network entity, a network device, or some other suitable term. The base station 102 may be implemented as an integrated access and backhaul (IAB) node, a relay node, a sidelink node, an aggregated (monolithic) base station with a baseband unit (BBU) (including a CU and a DU) and a RU, or as a disaggregated base station including one or more of a CU, a DU, and / or a RU. A set of base stations that may include disaggregated base stations and / or aggregated base stations may be referred to as a next generation (NG) RAN (NG-RAN).

[0062] The core network 120 may include an access and mobility management function (AMF) 161, a session management function (SMF) 162, a user plane function (UPF) 163, a unified data management (UDM) 164, one or more location servers 168, and other functional entities. AMF 161 is a control node for processing signaling between UE 104 and the core network 120. AMF 161 supports registration management, connection management, mobility management, and other functions. SMF 162 supports session management and other functions. UPF 163 supports packet routing, packet forwarding, and other functions. UDM 164 supports the generation of authentication and key agreement (AKA) credentials, user identity processing, access authorization, and subscription management. One or more location servers 168 are shown as including a gateway mobile location center (GMLC) 165 and a location management function (LMF) 166. However, in general, the one or more location servers 168 may include one or more location / positioning servers, which may include one or more of the GMLC 165, LMF 166, position determination entity (PDE), serving mobile location center (SMLC), mobile positioning center (MPC), etc. GMLC 165 and LMF 166 support UE location services. GMLC 165 provides an interface for accessing UE positioning information for clients / applications (e.g., emergency services). LMF 166 receives measurement and assistance information from NG-RAN and UE 104 via AMF 161 to calculate the location of UE 104. NG-RAN can determine the location of UE 104 using one or more positioning methods. Positioning UE 104 may involve signal measurements, position estimation, and optional speed calculation based on measurements. Signal measurements may be performed by UE 104 and / or serving base station 102. The measured signal may be based on a satellite positioning system (SPS) 170 (e.g., one or more of a global navigation satellite system (GNSS), a global positioning system (GPS), a non-terrestrial network (NTN), or other satellite positioning / positioning systems), LTE signals, wireless local area network (WLAN) signals, Bluetooth signals, a terrestrial beacon system (TBS), sensor-based information (e.g., air pressure sensor, motion sensor), NR enhanced cell ID (NRE-CID) method, NR signal (e.g., multi-round trip time (multi-RTT), DL transmission angle (DL-AoD), DL arrival time difference (DL-TDOA), UL arrival time difference (UL-TDOA), and UL incidence angle (UL-AoA) positioning) and / or other systems / signals / sensors.

[0063] Examples of UE 104 include cellular phones, smart phones, session initiation protocol (SIP) phones, laptop computers, personal digital assistants (PDAs), satellite radio units, global positioning systems, multimedia devices, video devices, digital audio players (e.g., MP3 players), cameras, game consoles, tablet devices, smart devices, wearable devices, vehicles, electric meters, gas pumps, large or small kitchen appliances, healthcare equipment, implants, sensors / actuators, displays, or any other similarly functional devices. Some of UE 104 may be referred to as IoT devices (e.g., parking meters, gas pumps, toasters, vehicles, heart monitors, etc.). UE 104 may also be referred to as stations, mobile stations, subscriber stations, mobile units, subscriber units, wireless units, remote units, mobile devices, wireless devices, wireless communication devices, remote devices, mobile subscriber stations, access terminals, mobile terminals, wireless terminals, remote terminals, handheld devices, user agents, mobile clients, clients, or some other appropriate terminology. In some scenarios, the term UE may also be applied to one or more companion devices, such as in a device constellation arrangement. One or more of these devices may access the network collectively and / or individually.

[0064] Reference again Figure 1, in some aspects, the UE 104 may include a PDU discard component 198 configured to transmit a plurality of PDUs associated with a DRB with a second wireless device; detect that at least one of the plurality of PDUs associated with the DRB satisfies at least one discard criterion; and send a discard status report associated with the at least one PDU that satisfies the at least one discard criterion to the second wireless device. In some aspects, the PDU discard component 198 is configured to transmit a plurality of PDUs associated with a DRB with a first wireless device; receive a discard status report associated with at least one of the plurality of PDUs that satisfies at least one discard criterion from the first wireless device; and update a sliding window of the DRB based on the discard status report. In some aspects, the PDU discard component 198 is configured to transmit a plurality of PDUs associated with a DRB with a second wireless device; receive an indication of a sequence number gap associated with at least one of the plurality of PDUs from the second wireless device based on expiration of a PDCP discard timer; and update a sliding window of the DRB based on the sequence number gap. In some aspects, the PDU discard component 198 is configured to transmit a plurality of PDUs associated with a DRB with a first wireless device; detect expiration of a PDCP discard timer associated with at least one PDU of the plurality of PDUs; and send an indication of a sequence number gap associated with at least one PDU of the plurality of PDUs to the first wireless device based on the expiration of the PDCP discard timer. In some aspects, the base station 102 may include a PDU discard component 199 configured as XYZ. In some aspects, the PDU discard component 199 is configured to transmit a plurality of PDUs associated with a DRB with a second wireless device; detect that at least one PDU of the plurality of PDUs associated with the DRB satisfies at least one discard criterion; and send a discard status report associated with the at least one PDU satisfying the at least one discard criterion to the second wireless device. In some aspects, the PDU discard component 199 is configured to transmit a plurality of PDUs associated with a DRB with a first wireless device; receive a discard status report associated with at least one PDU of the plurality of PDUs satisfying at least one discard criterion from the first wireless device; and update a sliding window of the DRB based on the discard status report. In certain aspects, the PDU discard component 199 is configured to transmit multiple PDUs associated with the DRB to a second wireless device; based on expiration of a PDCP discard timer, receive an indication of a sequence number gap associated with at least one PDU in the multiple PDUs from the second wireless device; and update a sliding window of the DRB based on the sequence number gap.In certain aspects, the PDU discard component 199 is configured to transmit a plurality of PDUs associated with the DRB with a first wireless device; detect expiration of a PDCP discard timer associated with at least one of the plurality of PDUs; and send an indication of a sequence number gap associated with at least one of the plurality of PDUs to the first wireless device based on the expiration of the PDCP discard timer. Although the following description may focus on 5G NR, the concepts described herein may be applicable to other similar fields, such as LTE, LTE-A, CDMA, GSM, and other wireless technologies.

[0065] Figure 2A FIG200 is a diagram showing an example of a first subframe within a 5G NR frame structure. Figure 2B FIG230 is a diagram showing an example of DL channels within a 5G NR subframe. Figure 2C FIG250 is a diagram showing an example of a second subframe within a 5G NR frame structure. Figure 2D FIG280 is a diagram showing an example of UL channels within a 5G NR subframe. The 5G NR frame structure can be frequency division duplex (FDD) (wherein, for a particular set of subcarriers (carrier system bandwidth), subframes within the subcarrier set are dedicated to either DL or UL), or can be time division duplex (TDD) (wherein, for a particular set of subcarriers (carrier system bandwidth), subframes within the subcarrier set are dedicated to both DL and UL). Figure 2A , 2C In the example provided, it is assumed that the 5G NR frame structure is TDD, subframe 4 is configured with slot format 28 (mostly DL), where D is DL, U is UL, and F can be used flexibly between DL / UL, and subframe 3 is configured with slot format 1 (all UL). Although subframes 3 and 4 are shown with slot formats 1 and 28, respectively, any particular subframe can be configured with any of the various available slot formats 0-61. Slot formats 0 and 1 are all DL and all UL, respectively. Other slot formats 2-61 include a mix of DL, UL and flexible symbols. The UE is configured with the slot format (dynamically configured by DL control information (DCI) or semi-statically / statically controlled by radio resource control (RRC) signaling) through the received slot format indicator (SFI). Note that the following description also applies to the 5G NR frame structure that is TDD.

[0066] Figures 2A-2DA frame structure is shown, and aspects of the present disclosure may be applicable to other wireless communication technologies that may have different frame structures and / or different channels. A frame (10ms) may be divided into 10 subframes (1ms) of equal size. Each subframe may include one or more time slots. A subframe may also include a microslot, which may include 7, 4 or 2 symbols. Each time slot may include 14 or 12 symbols, depending on whether the cyclic prefix (CP) is normal or extended. For a normal CP, each time slot may include 14 symbols, and for an extended CP, each time slot may include 12 symbols. The symbol on the DL may be a CP orthogonal frequency division multiplexing (OFDM) (CP-OFDM) symbol. The symbol on the UL may be a CP-OFDM symbol (for high throughput scenarios) or a discrete Fourier transform (DFT) spread OFDM (DFT-s-OFDM) symbol (also known as a single carrier frequency division multiple access (SC-FDMA) symbol) (for power-limited scenarios; limited to single stream transmission). The number of time slots within a subframe is based on the CP and the digital scheme. The digital scheme defines a subcarrier spacing (SCS) (see Table 1). The symbol length / duration can be scaled by 1 / SCS.

[0067]

[0068] Table 1: Digital scheme, SCS and CP

[0069] For normal CP (14 symbols / slot), different digital schemes μ0 to 4 allow 1, 2, 4, 8, and 16 slots per subframe, respectively. For extended CP, digital scheme 2 allows 4 slots per subframe. Therefore, for normal CP and digital scheme μ, there are 14 symbols / slot and 2 μ timeslots / subframe. The subcarrier spacing can be equal to 2 μ *15kHz, where μ is the digital scheme 0 to 4. As such, digital scheme μ=0 has a subcarrier spacing of 15kHz, and digital scheme μ=4 has a subcarrier spacing of 240kHz. The symbol length / duration is inversely related to the subcarrier spacing. Figures 2A-2D An example of a digital scheme μ=2 with a normal CP of 14 symbols per slot and 4 slots per subframe is provided. The slot duration is 0.25 ms, the subcarrier spacing is 60 kHz, and the symbol duration is about 16.67 μs. Within a frame set, there may be one or more different bandwidth parts (BWPs) that are frequency-division multiplexed (see Figure 2B ). Each BWP can have a specific numbering scheme and CP (normal or extended).

[0070] The frame structure can be represented using a resource grid. Each time slot includes a resource block (RB), also called a physical RB (PRB), which extends over 12 consecutive subcarriers. The resource grid is divided into multiple resource elements (REs). The number of bits carried by each RE depends on the modulation scheme.

[0071] like Figure 2A As shown in , some of the REs carry reference (pilot) signals (RS) for the UE. The RS may include a demodulation RS (DM-RS) (indicated as R for one particular configuration, but other DM-RS configurations are possible) and a channel state information reference signal (CSI-RS) for channel estimation at the UE. The RS may also include a beam measurement RS (BRS), a beam refinement RS (BRRS), and a phase tracking RS (PT-RS).

[0072] Figure 2B An example of various DL channels within a subframe of a frame is illustrated. A physical downlink control channel (PDCCH) carries DCI within one or more control channel elements (CCEs) (e.g., 1, 2, 4, 8, or 16 CCEs), each CCE including six RE groups (REGs), each REG including 12 consecutive REs in one OFDM symbol of an RB. A PDCCH within a BWP may be referred to as a control resource set (CORESET). The UE is configured to monitor PDCCH candidates in a PDCCH search space (e.g., a common search space, a UE-specific search space) during a PDCCH monitoring opportunity on a CORESET, wherein the PDCCH candidates have different DCI formats and different aggregation levels. Additional BWPs may be located at higher and / or lower frequencies on the channel bandwidth. A primary synchronization signal (PSS) may be within symbol 2 of a particular subframe in a frame. The PSS is used by UE 104 to determine subframe / symbol timing and physical layer identity. A secondary synchronization signal (SSS) may be located within symbol 4 of a particular subframe of a frame. The SSS is used by the UE to determine the physical layer cell identity group number and the radio frame timing. Based on the physical layer identity and the physical layer cell identity group number, the UE can determine the physical cell identifier (PCI). Based on the PCI, the UE can determine the location of the DM-RS. The physical broadcast channel (PBCH) carrying the master information block (MIB) can be logically grouped with the PSS and SSS to form a synchronization signal (SS) / PBCH block (also called SS block (SSB)). The MIB provides the number of RBs in the system bandwidth and the system frame number (SFN). The physical downlink shared channel (PDSCH) carries user data, broadcast system information not sent via the PBCH (e.g., system information block (SIB)), and paging messages.

[0073] like Figure 2CAs shown, some REs carry DM-RS (denoted as R for one particular configuration, but other DM-RS configurations are possible) for channel estimation at the base station. The UE can send DM-RS for the physical uplink control channel (PUCCH) and DM-RS for the physical uplink shared channel (PUSCH). The PUSCH DM-RS can be sent in the first or first two symbols of the PUSCH. Depending on whether a short PUCCH or a long PUCCH is sent and depending on the specific PUCCH format used, the PUCCH DM-RS can be sent in different configurations. Although not shown, the UE can send a sounding reference signal (SRS). The SRS can be sent in the last symbol of the subframe. The SRS can have a comb structure, and the UE can send the SRS on one of the combs. The SRS can be used by the base station for channel quality estimation to achieve frequency-dependent scheduling of the UL.

[0074] Figure 2D An example of various UL channels within a subframe of a frame is illustrated. The PUCCH may be positioned as indicated in a configuration. The PUCCH carries uplink control information (UCI), such as scheduling requests, channel quality indicators (CQI), precoding matrix indicators (PMI), rank indicators (RI), and hybrid automatic repeat request (HARQ) acknowledgement (ACK) (HARQ-ACK) feedback (i.e., one or more HARQ ACK bits indicating one or more ACKs and / or negative ACKs (NACKs)). The PUSCH carries data and may additionally be used to carry buffer status reports (BSRs), power headroom reports (PHRs), and / or UCI.

[0075] Figure 33 is a block diagram of a base station 310 in an access network communicating with a UE 350. In the DL, Internet Protocol (IP) packets may be provided to a controller / processor 375. The controller / processor 375 implements the functions of layer 3 and layer 2. Layer 3 includes a radio resource control (RRC) layer, and layer 2 includes a service data adaptation protocol (SDAP) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The controller / processor 375 provides: RRC layer functions associated with: broadcasting of system information (e.g., MIB, SIB), RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), inter-radio access technology (RAT) mobility, and measurement configuration for UE measurement reporting; PDCP layer functions associated with: header compression / decompression, security (ciphering, deciphering, integrity protection, integrity verification), and handover support functions; RLC layer functions associated with: transmission of upper layer packet data units (PDUs), error correction through ARQ, concatenation, segmentation and reassembly of RLC service data units (SDUs), re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functions associated with: mapping between logical channels and transport channels, multiplexing of MAC SDUs onto transport blocks (TBs), MAC Demultiplexing of SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

[0076] The transmit (TX) processor 316 and the receive (RX) processor 370 implement layer 1 functions associated with various signal processing functions. Layer 1 (which includes the physical (PHY) layer) may include error detection on the transmission channel, forward error correction (FEC) encoding / decoding of the transmission channel, interleaving, rate matching, mapping to the physical channel, modulation / demodulation of the physical channel, and MIMO antenna processing. The TX processor 316 processes the mapping for the signal constellation diagram based on various modulation schemes (e.g., binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), M-phase phase shift keying (M-PSK), M-order quadrature amplitude modulation (M-QAM)). The coded and modulated symbols can then be divided into parallel streams. Subsequently, each stream can be mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., a pilot) in the time domain and / or frequency domain, and then combined using an inverse fast Fourier transform (IFFT) to generate a physical channel for carrying a time domain OFDM symbol stream. The OFDM stream is spatially precoded to generate multiple spatial streams. Channel estimates from a channel estimator 374 may be used to determine coding and modulation schemes, as well as spatial processing. Channel estimates may be derived based on reference signals and / or channel condition feedback sent by the UE 350. Each spatial stream may then be provided to a different antenna 320 via a separate transmitter 318Tx. Each transmitter 318Tx may modulate a radio frequency (RF) carrier with a corresponding spatial stream for transmission.

[0077] At the UE 350, each receiver 354Rx receives a signal through its corresponding antenna 352. Each receiver 354Rx recovers the information modulated onto the RF carrier and provides the information to a receive (RX) processor 356. The TX processor 368 and the RX processor 356 implement layer 1 functions associated with various signal processing functions. The RX processor 356 can perform spatial processing on the information to recover any spatial stream destined for the UE 350. If multiple spatial streams are destined for the UE 350, they can be merged into a single OFDM symbol stream by the RX processor 356. The RX processor 356 then uses a fast Fourier transform (FFT) to convert the OFDM symbol stream from the time domain to the frequency domain. The frequency domain signal includes a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols and reference signals on each subcarrier are recovered and demodulated by determining the most likely signal constellation point sent by the base station 310. These soft decisions can be based on the channel estimates calculated by the channel estimator 358. The soft decisions are then decoded and deinterleaved to recover the data and control signals originally sent on the physical channel by base station 310. The data and control signals are then provided to controller / processor 359, which implements layer 3 and layer 2 functionality.

[0078] The controller / processor 359 may be associated with a memory 360 that stores program codes and data. The memory 360 may be referred to as a computer readable medium. In the UL, the controller / processor 359 provides demultiplexing, packet reassembly, decryption, header decompression, and control signal processing between transport and logical channels to recover IP packets. The controller / processor 359 is also responsible for error detection using ACK and / or NACK protocols to support HARQ operations.

[0079] Similar to the functions described in conjunction with the DL transmission of the base station 310, the controller / processor 359 provides: RRC layer functions associated with system information (e.g., MIB, SIB) acquisition, RRC connection, and measurement reporting; PDCP layer functions associated with header compression / decompression and security (encryption, decryption, integrity protection, integrity verification); RLC layer functions associated with transmission of upper layer PDUs, error correction through ARQ, concatenation, segmentation and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; MAC layer functions associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority processing, and logical channel priority.

[0080] The TX processor 368 may use channel estimates derived by the channel estimator 358 from a reference signal or feedback transmitted by the base station 310 to select appropriate coding and modulation schemes and to facilitate spatial processing. The spatial streams generated by the TX processor 368 may be provided to different antennas 352 via respective transmitters 354Tx. Each transmitter 354Tx may modulate an RF carrier with a respective spatial stream for transmission.

[0081] The base station 310 processes the UL transmission in a manner similar to that described in conjunction with the receiver functionality at the UE 350. Each receiver 318Rx receives the signal through its respective antenna 320. Each receiver 318Rx recovers the information modulated onto the RF carrier and provides the information to the RX processor 370.

[0082] The controller / processor 375 may be associated with a memory 376 that stores program codes and data. The memory 376 may be referred to as a computer readable medium. In the UL, the controller / processor 375 provides demultiplexing between transport and logical channels, packet reassembly, decryption, header decompression, control signal processing to recover IP packets. The controller / processor 375 is also responsible for error detection using ACK and / or NACK protocols to support HARQ operations.

[0083] At least one of the TX processor 368, the RX processor 356, and the controller / processor 359 may be configured to perform operations related to Figure 1 Various aspects related to the PDU discard component 198.

[0084] At least one of the TX processor 316, the RX processor 370, and the controller / processor 375 may be configured to perform operations related to Figure 1 Various aspects related to the PDU discard component 199.

[0085] Figure 4 400 is a diagram illustrating an example XR service. XR services may refer to wireless communications for technologies such as virtual reality (VR), mixed reality (MR), and / or augmented reality (AR). VR may refer to a technology in which a user is immersed in a simulated experience similar to or different from the real world. A user may interact with a VR system through a VR headset or a multi-projection environment that generates realistic images, sounds, and other sensations that simulate the user's physical presence in a virtual environment. MR may refer to a technology that mixes aspects of a virtual environment with a real environment. AR may refer to a technology in which objects residing in the real world are enhanced via computer-generated sensory information, which is sometimes enhanced across multiple sensory modes, such as vision, hearing, touch, body sensation, and / or smell. AR systems may combine real and virtual worlds, real-time interactions, and precise three-dimensional registration of virtual objects and real objects. In an example, an AR system may overlay sensory information (e.g., images) onto a natural environment and / or shield real objects from the natural environment. XR services may include video data and / or audio data. The XR service may be transmitted by the base station and received by the UE, or the XR service may be transmitted by the UE and received by the base station.

[0086] XR services may have several significant features. First, XR services may arrive in periodic service bursts ("XR service bursts"). XR service bursts may vary in the number of packets per burst and / or the size of each packet in the burst. Figure 400 shows a first XR stream 402 that may include a first XR service burst 404 and a second XR service burst 406. As shown in Figure 400, the first XR service burst 404 may include three packets (represented as rectangles in Figure 400), and the second XR service burst 406 may include two packets. In addition, as shown in Figure 400, the three packets in the first XR service burst 404 and the two packets in the second XR service burst 406 may vary in size, that is, the packets within the first XR service burst 404 and the second XR service burst 406 may include a varying amount of data.

[0087] Secondly, XR service bursts may arrive in non-integer periods (i.e., in non-integer cycles). In an example, for video data at 60 frames per second (FPS), XR service bursts may arrive in a 1 / 60=16.67ms period. In another example, for video data at 120FPS, XR service bursts may arrive in a 1 / 120=8.33ms period.

[0088] Third, the arrival time of XR traffic may vary, that is, an XR traffic burst may arrive earlier or later than the time when the UE (or base station) expects the XR traffic burst. This may be referred to as "jitter". In an example, the jitter range of XR traffic may be from -4ms (arriving earlier than expected) to +4ms (arriving later than expected). For example, referring to the first XR stream 402, the UE may expect the first packet of the first XR traffic burst 404 to arrive at time t0, but the second packet of the first XR traffic burst 404 arrives at time t1.

[0089] Fourth, the XR service may include multiple streams that may arrive at the UE (or base station) concurrently with each other (or within a threshold time period). For example, diagram 400 includes a second XR stream 408. The second XR stream 408 may have different characteristics from the first XR stream 402. For example, the second XR stream 408 may have XR service bursts with different numbers of packets, packets of different sizes, and the like. In an example, the first XR stream 402 may include video data, and the second XR stream 408 may include audio data for the video data. In another example, the first XR stream 402 may include an intra-coded picture frame (I frame) containing a complete image, and the second XR stream 408 may include a predicted picture frame (P frame) including changes from a previous image.

[0090] Fifth, XR services may follow a packet delay budget (PDB). If a packet does not arrive within the PDB, the UE (or base station) may discard the packet. In an example, if a packet corresponding to a video frame of a video does not arrive at the UE within the PDB, the UE may discard the packet because the video has progressed beyond the frame.

[0091] Generally speaking, XR services can be characterized by relatively high data rates and low latency. For example, XR services may have applications in eMBB and URLLC services.

[0092] Figure 5500 is a diagram depicting an example of generating RLC PDUs 502, 504, 506 from RLC SDUs 508, 510, 512. The RLC entity may generate RLC PDUs 502-506 from the RLC SDUs 508-512. The SDU may refer to a payload within a PDU. In an example, the RLC entity may be an RLC receiver (e.g., RLC receiver 1402). In another example, the RLC entity may be an RLC transmitter (e.g., RLC transmitter 1404). As shown in Figure 500, the RLC entity may operate in an acknowledgement mode (AM), which may support segmentation, duplication removal, and retransmission of erroneous data. The RLC PDUs 502-506 may be associated with a data radio bearer (DRB) 514. The DRB 514 may be an AM DRB. The DRB 514 may be a logical transport "pipe" that carries the PDU from the core network and across the RAN to the UE.

[0093] The RLC entity may attach a header 516 (shown as "H" in Figure 500) to the RLC SDU 508-512 (or a fragment thereof) to generate an RLC PDU 502-506. The combination of the header and the RLC SDU may be referred to as an RLC PDU. The header 516 may include a data control indicator 518 (shown as "DC" in Figure 500), which may indicate whether the associated RLC PDU contains data to / from a logical channel or control information for RLC operation. The header 516 may include a polling bit 520 (shown as "P" in Figure 500) that may be used to request a status report. The header 516 may include a segmentation information field 522 (shown as "SI" in Figure 500), which indicates whether the associated RLC PDU is a complete RLC SDU, the first segment of the RLC SDU, the last segment of the RLC SDU, or a segment between the first and last segments of the RLC SDU. The header 516 may include an RLC SDU sequence number 524 (shown as "n" in diagram 500) of the SDU. If the header 516 is associated with a segmented RLC SDU, the header 516 may include a segment offset 526 (shown as "SO" in diagram 500) indicating which byte of the RLC SDU the RLC SDU segment represents.

[0094] For unsegmented RLC SDUs (e.g., RLC SDU 508 and RLC SDU 510), the RLC entity may append headers to the associated SDUs to generate RLC PDUs (e.g., RLC PDU 502 and RLC PDU 504). Due to MAC multiplexing, the size of the last RLC PDU in a transport block may not match the size of the RLC SDU. In this way, the RLC entity may segment the RLC SDU (e.g., RLC SDU 512) into a plurality of segments (e.g., SDU segment 528 and SDU segment 530), wherein each of the plurality of segments may include a corresponding header. In an example, the RLC entity may send the RLC PDUs 502-506 to the MAC layer for transmission in a first transport block. In this example, the RLC entity may send the RLC PDU associated with the SDU segment 530 to the MAC layer for transmission in a second transport block.

[0095] Figure 6 6 is a diagram 600 illustrating an example of an RLC transmitter 602 discarding a PDU. In the example depicted in diagram 600, the RLC transmitter 602 has discarded a PDU (e.g., PDU 3). If the RLC transmitter 602 does not notify the RLC receiver 604 of the discarded PDU, there may be a gap in the RLC SN at the RLC receiver 604. The gap may slow down the advancement of the receiver-side sliding window 606 by the RLC receiver 604. For example, if the RLC transmitter 602 does not notify the RLC receiver 604 of the discarded PDU, the RLC receiver 604 may wait to receive the (discarded) PDU. Waiting to receive the (discarded) PDU may delay the RLC receiver 604 from sending an acknowledgment to the RLC transmitter 602, which may delay further transmissions by the RLC transmitter 602.

[0096] Figure 7 700 is a diagram showing an example of an RLC receiver 702 discarding a PDU. A PDU may refer to a data packet sent in a 3GPP network. In the example shown in diagram 700, an RLC transmitter 704 has sent PDUs 1-5. However, the RLC receiver 702 has discarded PDU 3 based on various criteria (described in more detail below). If the RLC receiver 702 discards the PDU but does not notify the RLC transmitter 704, the RLC transmitter 704 may not advance the transmitter side sliding window 706. If the RLC transmitter 704 does not advance the transmitter side sliding window 706, further transmissions of the RLC transmitter 704 may be delayed.

[0097] In the L2 process, various types of events can trigger PDU discarding. For example, if a PDU misses a configured delay budget or a signaled delivery deadline, the PDU may become obsolete. PDU discarding can be triggered by intra-PDU set dependency. In one example, a PDU set can be configured so that each PDU in the PDU set will be sent or received. If a PDU in a PDU set is discarded, other PDUs in the PDU set may also be discarded. In another example, if a PDU in a PDU set is discarded, subsequent PDUs in the PDU set may also be discarded. PDU discarding can also be triggered by inter-frame dependency (which may be referred to as inter-PDU set dependency because a frame may include one or more PDU sets). In an example, there may be dependencies between PDUs in a quality of service (QoS) stream. For example, a predicted picture frame (p frame) in a decoded video stream may depend on an intra-frame decoded picture frame (I frame) in the same burst. If the UE discards an I frame, the UE may also discard the associated P frame because such a frame may be obsolete. If the RLC receiver discards the PDU but does not notify the RLC transmitter of the discard, the RLC transmitter may not advance the transmitter side ARQ window. This may delay further transmissions by the RLC transmitter. If the RLC transmitter discards the PDU but does not notify the RLC receiver of the discard, there may be gaps in the RLC PDU SNs. This may delay the advancement of the receiver side ARQ window.

[0098] Various techniques related to PDU discarding are described herein. In an example, a first wireless device transmits a plurality of PDUs associated with a DRB with a second wireless device. The first wireless device detects that at least one of the plurality of PDUs associated with the DRB satisfies at least one discard criterion. The discard criterion may be a set of criteria used by the UE to determine when / whether to discard a PDU. The first wireless device sends a discard status report associated with at least one PDU that satisfies at least one discard criterion to the second wireless device. The discard status report may include an indication of which PDUs have been discarded. The second wireless device may update a sliding window based on the discard status report. Thus, the discard status report may prevent transmission stagnation of the second wireless device and may thus result in increased communication reliability at the first wireless device. In another example, the first wireless device transmits a plurality of PDUs associated with the DRB with a second wireless device. The first wireless device receives an indication of a sequence number gap associated with at least one of the plurality of PDUs from the second wireless device based on expiration of a PDCP discard timer. The first wireless device updates a sliding window of the DRB based on the sequence number gap. Thus, the indication of the sequence number gap may help the first wireless device update the sliding window and may result in increased communication reliability at the first wireless device.

[0099] Fig.14 1400 is a diagram depicting communication between an RLC receiver 1402 and an RLC transmitter 1404. In one example, the RLC receiver 1402 may be a UE (e.g., UE 104, UE 350, device 2304, etc.), and the RLC transmitter 1404 may be a base station (e.g., base station 102, base station 310, network entity 2402, etc.). In another example, the RLC receiver 1402 may be a base station (e.g., base station 102, base station 310, network entity 2402, etc.), and the RLC transmitter 1404 may be a UE (e.g., UE 104, UE 350, device 2304, etc.).

[0100] In one aspect, the RLC receiver 1402 may discard the RLC PDU. For example, at 1406, the RLC receiver 1402 may receive a timer configuration sent by the RLC transmitter 1404. In one example, the timer configuration may be used to configure a state prohibit timer. The state prohibit timer may be associated with (e.g., triggered by) the lost RLC PDU. When the state prohibit timer is active, the RLC receiver 1402 may send a status report no more than once per time interval determined by the state prohibit timer. In another example, the timer configuration may be used to configure a state report prohibit timer. The state report prohibit timer may be associated with (e.g., triggered by) the RLC PDU discard. When the state report prohibit timer is active, the RLC receiver 1402 may send a status report no more than once per time interval determined by the state report prohibit timer. The state prohibit timer and the state report prohibit timer may be associated with different corresponding time intervals. At 1408, the RLC receiver 1402 may configure the timer based on the timer configuration received at 1406.

[0101] At 1410, the RLC receiver 1402 may receive an RLC PDU sent by the RLC transmitter 1404. For example, the RLC PDU may be or include the RLC PDUs 502-506 in Figure 500. In an example, the RLC PDU may be associated with an XR service. For example, the RLC PDU may be associated with the XR service shown in Figure 400. At 1414, the RLC receiver 1402 may determine that an RLC PDU (or more than one RLC PDU) in the RLC PDU will be discarded based on a criterion. The criterion may include one or more of an intra-PDU set dependency, a missed delay deadline for receiving the RLC PDU, a stream error correction (FEC) decoding redundancy rate above a decoding threshold, or an inter-frame dependency. In an example, the intra-PDU set dependency may refer to a PDU lost in a PDU set. If a PDU is lost in a PDU set (e.g., because the PDU is not successfully received), the entire set of PDUs may be discarded. In an example, FEC may refer to a class of codes with a unique property: a set of data packets may be decoded into N transmitted data packets, so that as long as K is less than N packets, a set of (original) data packets may be recovered, where K and N may be integers. The ratio of N to K may be referred to as the redundancy rate, i.e., how much redundancy may be used to protect the original data. In an example of intra-frame dependency, a video may be decoded by several PDUs (or a collection of PDUs). In some coding schemes, the encoding of a PDU may depend on a certain frame before the PDU. For example, the second frame in a frame may include a difference ("delta") from the first PDU in the frame. This may be referred to as intra-frame dependency. At 1416, the RLC receiver 1402 may discard the RLC PDU based on the RLC PDU satisfying a criterion. For example, the RLC receiver 1402 may discard the RLC SDU associated with the RLC PDU. In an example where the RLC PDU 502 is discarded, the RLC receiver 1402 may discard the RLC SDU 508. In another example where the RLC PDU 506 is discarded, the RLC receiver 1402 may discard the SDU segment 528 and the SDU segment 530 .

[0102] When the RLC receiver 1402 determines that an RLC PDU or RLC SDU segment in an AM DRB is to be discarded, the RLC receiver 1402 may trigger the sending of a discard status report to the RLC transmitter 1404. The discard status report may include an indication of the SN of the (discarded) RLC PDU. The RLC receiver 1402 may send the discard status report to the RLC transmitter 1404 according to a timer configured at 1408 (e.g., a status prohibit timer or a status report prohibit timer), that is, the RLC receiver 1402 may send the discard status report once per time interval determined by the timer.

[0103] In some aspects, the discard status report sent by the RLC receiver 1402 may utilize the format used for missing PDU reporting, i.e., the RLC receiver 1402 may reuse the format to report discarded RLC PDUs. Figure 8 An example status report 800 for missing PDU reporting is shown. Status report 800 may be referred to as a discard status report. Status report 800 may be used for an RLC entity configured with a 12-bit SN. Status report 800 may be organized according to octets. In one example, status report 800 may not include an indication of whether status report 800 is triggered by RLC PDU discard or by reception of an RLC PDU.

[0104] Status report 800 may include an indication as to whether status report 800 is for RLC control or for RLC data (e.g. Figure 8 The status report 800 may include a field indicating that the status report is related to the status (in Figure 8 Status report 800 may include reserved bits (such as Figure 8 The status report 800 may include an E field (in Figure 8 The E field includes information about whether the status report 800 includes the SN of the RLC PDU that has been detected as lost (shown as "E1", "E2" and "E3" in FIG. Figure 8 ) and the information including the SN (in Figure 8 The status report may include an indication of a portion of an RLC PDU that is missing (collectively referred to as "SOstart" and "SOend" in the READ_SCHEMA_01). The status report may include an indication of a missing RLC SDU (in the READ_SCHEMA_01). Figure 8 The status report 800 may include an ACK_SN 802. The ACK_SN 802 may be the SN of the RLC PDU that was discarded. In an example, the ACK_SN 802 may be the SN of the RLC PDU that was discarded by the RLC receiver 1402 at 1416.

[0105] Fig. 914 is a diagram showing another example of a status report 900 for missing RLC PDU reporting, i.e., the RLC receiver 1402 may re-use the format to report discarded RLC PDUs. The status report 900 may be referred to as a discard status report. The status report 900 may be used for an RLC entity configured with an 18-bit SN. The ACK_SN 902 in the status report 900 may be used for a similar purpose as the ACK_SN 802 in the status report 800 described above, i.e., the ACK_SN 902 may be the SN of the discarded RLC PDU. In the example, the ACK_SN 902 may be the SN of the RLC PDU discarded by the RLC receiver 1402 at 1416. The status report 900 may also include the ACK_SN 802 as described above in the status report 800. Figure 8 “D / C”, “CPT”, “R”, “E1”, “E2”, “E3”, “NACK_SN”, “SOstart”, “SOend” and “NACK range” described in the description of .

[0106] In some aspects, the status report sent by the RLC receiver 1402 may utilize a format for RLC PDU discard. Fig.10 1 is a diagram illustrating an example of a status report 1000 for RLC PDU discard. Status report 1000 may be referred to as a discard status report. Status report 1000 may be for an RLC entity configured with a 12-bit SN. Status report 1000 may be similar to status report 800 described above. However, status report 1000 may include an E4 field 1002 (instead of a reserved bit). E4 field 1002 may include a bit indicating whether status report 1000 includes an indication of RLC PDU discard. When E4 field 1002 is set to true, status report 1000 may include DISCARD_SN 1004. DISCARD_SN 1004 may be the SN of the RLC PDU that was discarded. In an example, DISCARD_SN 1004 may be the SN of the RLC PDU discarded by RLC receiver 1402 at 1416. Status report 1000 may also include a SN as described above in Figure 8 The “D / C”, “CPT”, “R”, “E1”, “E2”, “E3”, “NACK_SN”, “SOstart”, “SOend” and “NACK range” described in the description of the status report 800. Unlike the status report 800, the status report 1000 can indicate whether the status report 1000 is triggered by RLC PDU discard or by reception of an RLC PDU.

[0107] Fig.111402 is a diagram illustrating another example of a status report 1100 for RLC PDU discard. Status report 1100 may be referred to as a discard status report. Status report 1100 may be for an RLC entity configured with an 18-bit SN. Status report 1100 may be similar to status report 900 described above. However, status report 1100 may include an E4 field 1102 (instead of a reserved bit). E4 field 1102 may include a bit indicating whether status report 1100 includes an indication of RLC PDU discard. When E4 field 1102 is set to true, status report 1100 may include DISCARD_SN 1104. DISCARD_SN 1104 may be the SN of the RLC PDU that was discarded. In an example, DISCARD_SN 1104 may be the SN of the RLC PDU discarded by RLC receiver 1402 at 1416. Status report 1100 may also include the status report 900 described above. Figure 8 "D / C", "CPT", "R", "E1", "E2", "E3", "NACK_SN", "SOstart", "SOend" and "NACK range" described in the description of status report 900. Unlike status report 900, status report 1100 can indicate whether status report 1100 is triggered by RLC PDU discard or by reception of RLC PDU.

[0108] Upon receiving the discard status report sent at 1418 at 1419 and if the discard status report is for RLC PDU discard (e.g., the discard status report is based on the status report 1000 or the status report 1100), the RLC transmitter 1404 may send an indication to one or more upper layers (e.g., the PDCP layer) about the RLC layer indicating that the RLC SDU in the discard status report has been discarded by the RLC receiver 1402. At 1420, the RLC transmitter 1404 may advance a transmitter sliding window (e.g., the transmitter side sliding window 706) based on the discard status report sent by the RLC receiver 1402 at 1418. In an example, the RLC transmitter 1404 may advance the transmitter sliding window based on the SN of the discarded RLC PDU included in the discard status report. In an example, the discard status report may be similar or identical to the above-described status report 800, status report 900, status report 1000, or status report 1100. The transmitter sliding window may be an ARQ sliding window.

[0109] In an example, the RLC transmitter 1404 may maintain an acknowledgment state variable ("TX_Next_Ack") that may hold the value of the SN of the next RLC SDU for which a positive acknowledgment will be received in sequence. TX_Next_Ack may be used as a lower boundary of a transmitter sliding window. The RLC transmitter 1404 may also maintain a transmit state variable ("TX_Next") that may hold the value of the SN to be assigned to the next newly generated RLC PDU. In this example, the RLC transmitter 1404 may update the transmitter sliding window as follows. The RLC transmitter 1404 may 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 and for which a positive acknowledgment has not yet been received.

[0110] In one aspect, the RLC transmitter 1404 may discard the RLC PDU. Fig.14 At 1422, the RLC transmitter 1404 may configure an inhibit timer. In an example, the inhibit timer may be a PDCP discard timer. In an example, the RLC transmitter 1404 may configure the inhibit timer based on a configuration from the network. At 1424, the RLC transmitter 1404 may obtain (e.g., generate, receive, etc.) an RLC PDU. In an example, the RLC PDU may be associated with the XR service shown in diagram 400.

[0111] At 1426, the RLC transmitter 1404 may obtain a discard indication from the PDCP layer (or another layer higher than the RLC layer) indicating that an RLC PDU (or multiple RLC PDUs) in the RLC PDU is to be discarded. Discarding the RLC PDU may result in a gap in the SN of the RLC PDU that has not yet been acknowledged by the RLC receiver 1402. At 1428, the RLC transmitter 1404 may discard the RLC PDU based on the discard indication. For example, the RLC transmitter 1404 may discard the RLC SDU associated with the RLC PDU. In an example where the RLC PDU 502 is discarded, the RLC transmitter 1404 may discard the RLC SDU 508. In another example where the RLC PDU 506 is discarded, the RLC transmitter 1404 may discard the SDU segment 528 and the SDU segment 530.

[0112] When the RLC transmitter 1404 obtains a discard indication from the PDCP layer at 1426, the inhibit timer (configured at 1422) may start running. While the inhibit timer is running, the RLC transmitter 1404 may refrain from sending a discard indication (e.g., the RLC receiver 1404 may maintain the discard indication). At 1429, the RLC transmitter 1404 may detect that the inhibit timer has expired. When the inhibit timer expires, at 1430, the RLC transmitter 1404 may send a discard indication control PDU to the RLC receiver 1402. The discard indication control PDU may include the SN of the RLC PDU discarded at 1428.

[0113] Fig.12 An example discard indication control PDU 1200 is shown. In an example, when the inhibit timer expires, the RLC transmitter 1404 may send the discard indication control PDU 1200 at 1430. The discard indication control PDU 1200 may be configured by an RLC entity configured with a 12-bit SN. The discard indication control PDU 1200 may be organized into octets.

[0114] The discard indication control PDU 1200 may include a D / C field 1202 indicating whether the discard indication control PDU 1200 is for data purpose or for control purpose. In an example, the D / C field 1202 may include a "1" bit to indicate that the discard indication control PDU 1200 is a control PDU. The discard indication control PDU 1200 may include a CPT field 1204 indicating the type of the control PDU. In an example, the CPT field 1204 may indicate that the discard indication control PDU 1200 is a discard indication. The discard indication control PDU 1200 may include a DISCARD_SN 1206 including the SN of the discarded RLC PDU. The discard indication control PDU 1200 may include an E1 field 1210 including a bit indicating whether an additional discard indication follows in the discard indication control PDU 1200. Unlike a status report, the discard indication control PDU 1200 may not include segmentation information because when a PDU is to be discarded, all segments in the PDU may be discarded.

[0115] Fig.13 An example discard indication control PDU 1300 is shown. In an example, when the inhibit timer expires, the RLC transmitter 1404 may send the discard indication control PDU 1300 at 1430. The discard indication control PDU 1300 may be configured by an RLC entity configured with an 18-bit SN. The discard indication control PDU 1300 may be organized into octets.

[0116] The discard indication control PDU 1300 may include a D / C field 1302 indicating whether the discard indication control PDU 1300 is for data purpose or for control purpose. In an example, the D / C field 1302 may include a "1" bit to indicate that the discard indication control PDU 1300 is a control PDU. The discard indication control PDU 1300 may include a CPT field 1304 indicating the type of the control PDU. In an example, the CPT field 1304 may indicate that the discard indication control PDU 1300 is a discard indication. The discard indication control PDU 1300 may include a DISCARD_SN 1306 including the SN of the discarded RLC PDU. The discard indication control PDU 1300 may include an E1 field 1310 including a bit indicating whether an additional discard indication follows in the discard indication control PDU 1300. Unlike a status report, the discard indication control PDU 1300 may not include segmentation information because when a PDU is to be discarded, all segments in the PDU may be discarded.

[0117] At 1432, the RLC receiver 1402 may advance a receiver sliding window (e.g., the receiver side sliding window 606) based on the discard indication control PDU. For example, the RLC receiver 1402 may advance the receiver sliding window based on the SN of the discarded RLC PDU included in the discard indication control PDU. The receiver sliding window may be an ARQ sliding window.

[0118] In an example, the RLC receiver 1402 may maintain a receive state variable ("Rx_Next") that holds the value of the SN following the last RLC SDU fully received in sequence. RX_Next may be used as a lower boundary of a receiver sliding window. The RLC receiver 1402 may also maintain a maximum STATUS send state variable ("RX_Higest_STATUS") that may hold the highest possible value of the SN that may be indicated by the ACK_SN when constructing a STATUS PDU. In this example, the RLC receiver 1402 may update the receiver sliding window as follows. The RLC receiver 1402 may receive a discard indication control PDU for an RLC PDU having an SN x, where x is an integer. If x is equal to Rx_Highest_Status, the RLC receiver 1402 may update Rx_Highest_Status to have an SN of a first RLC SDU having an SN greater than a current Rx_Highest_Status for which all bytes have not yet been received. If x is equal to RX_Next, the RLC receiver 1402 may update RX_Next to have the SN of the first RLC SDU having a greater SN than the current RX_Next for which all bytes have not been received.

[0119] Fig.15 1500 is a flow chart of a method of wireless communication at a first wireless device. The method may be performed by an RLC receiver (e.g., RLC receiver 1402). The RLC receiver may be a UE (e.g., UE 104, UE 350, apparatus 2304). The RLC receiver may be a network entity (e.g., base station 102, CU 110, DU 130, RU 140, base station 310, network entity 2402). In an example, the method may be performed by PDU discard component 198 or PDU discard component 199. The method is associated with increased communication reliability of UE and / or network entity.

[0120] At 1502, a first wireless device transmits a plurality of PDUs associated with a DRB with a second wireless device. Fig.14 At 1410, it is shown that the RLC receiver 1402 can receive a PDU from the RLC transmitter 1404. In an example, the PDU can be or include RLC PDUs 502-506. In another example, multiple PDUs can be sent to the same Figure 5 1502 may be associated with the DRB 514 shown in . For example, 1502 may be performed by the PDU discarding component 198 or the PDU discarding component 199.

[0121] At 1504, the first wireless device detects that at least one PDU of a plurality of PDUs associated with the DRB satisfies at least one discard criterion. Fig.14 At 1414, it is shown that the RLC receiver 1402 can determine based on the criteria that the PDU is to be discarded. In another example, the PDU can be one or more of the RLC PDUs 502-506. For example, 1504 can be performed by the PDU discard component 198 or the PDU discard component 199.

[0122] At 1506, the first wireless device sends a discard status report associated with at least one PDU that satisfies at least one discard criterion to the second wireless device. Fig.14 At 1418, the RLC receiver may send a discard status report. In an example, the discard status report may be sent at Figure 8 , 9 , 10 and 11 respectively shown in the status report 800, the status report 900, the status report 1000 or the status report 1100. For example, 1506 can be performed by the PDU discarding component 198 or the PDU discarding component 199.

[0123] Fig.16 1600 is a flow chart of a method of wireless communication at a first wireless device. The method (including various aspects detailed below) may be performed by an RLC receiver (e.g., RLC receiver 1402). The RLC receiver may be a UE (e.g., UE 104, UE 350, apparatus 2304). The RLC receiver may be a network entity (e.g., base station 102, CU 110, DU 130, RU 140, base station 310, network entity 2402). In an example, the method (including various aspects detailed below) may be performed by PDU discard component 198 or PDU discard component 199. The method is associated with increased communication reliability of UE and / or network entity.

[0124] At 1604, the first wireless device transmits a plurality of PDUs associated with the DRBs with the second wireless device. For example, Fig.14 At 1410, it is shown that the RLC receiver 1402 can receive a PDU from the RLC transmitter 1404. In an example, the PDU can be or include RLC PDUs 502-506. In another example, multiple PDUs can be sent to the same Figure 5 1604 may be performed by the PDU discarding component 198 or the PDU discarding component 199, for example.

[0125] At 1606, the first wireless device detects that at least one PDU of the plurality of PDUs associated with the DRB satisfies at least one discard criterion. Fig.14At 1414, it is shown that the RLC receiver 1402 can determine based on the criteria that the PDU is to be discarded. In another example, the PDU can be one or more of the RLC PDUs 502-506. For example, 1606 can be performed by the PDU discard component 198 or the PDU discard component 199.

[0126] At 1610, the first wireless device sends a discard status report associated with at least one PDU that satisfies at least one discard criterion to the second wireless device. Fig.14 At 1418, the RLC receiver 1402 may send a discard status report. In an example, the discard status report may be sent at Figure 8 , 9 , 10 and 11 respectively show the status report 800, the status report 900, the status report 1000 or the status report 1100. For example, 1610 can be performed by the PDU discarding component 198 or the PDU discarding component 199.

[0127] In one aspect, the at least one discard criterion may include one or more of the following: intra-PDU set dependency, missed delay deadline, FEC decoding redundancy rate above a decoding threshold, or inter-frame dependency. Fig.14 The criteria shown at 1414 may include intra-PDU set dependency, missed delay deadline, FEC coding redundancy rate above a decoding threshold, and / or inter-frame dependency.

[0128] In one aspect, at 1608, the first wireless device may discard the at least one PDU upon detecting that the at least one PDU satisfies at least one discard criterion. For example, Fig.14 At 1416, it is shown that the RLC receiver 1402 can discard the PDU. In an example, the PDU can be one or more of the RLC PDUs 502-506. In another example, Figure 7 The RLC receiver 702 is shown discarding the PDU. For example, 1608 can be performed by the PDU discard component 198 or the PDU discard component 199.

[0129] In one aspect, at 1608A, discarding the at least one PDU may include discarding each of a set of RLC SDUs associated with the at least one PDU. For example, the set of RLC SDUs may be RLC SDUs 508-512. For example, 1608A may be performed by PDU discard component 198 or PDU discard component 199.

[0130] In one aspect, the DRB may be an AM DRB. For example, Figure 5 A DRB 514 is shown which may be an AM DRB.

[0131] In one aspect, at 1602, the first wireless device may receive a configuration for a status prohibit timer associated with a lost PDU or a status report prohibit timer associated with a PDU discard, wherein a discarded status report is associated with the status prohibit timer or the status report prohibit timer. Fig.14 At 1406, it is shown that the RLC receiver 1402 can receive a timer configuration. The timer configuration can be associated with a status prohibit timer or a status report prohibit timer. For example, 1602 can be performed by the PDU discard component 198 or the PDU discard component 199.

[0132] In one aspect, the discard status report may be sent at a time corresponding to the expiration of a status prohibit timer or a status report prohibit timer. Fig.14 It is shown that the RLC receiver 1402 can send a discard status report according to the timer rules.

[0133] In one aspect, the discard status report may utilize an acknowledgment field to indicate at least one sequence number of at least one PDU. For example, the acknowledgment field may be Figure 8 and Fig. 9 ACK_SN 802 or ACK_SN 902 shown in FIG.

[0134] In one aspect, the discard status report may include at least one additional field compared to at least one other discard status report, wherein the at least one additional field may include at least one sequence number of the at least one PDU. For example, the at least one additional field may include the E4 field 1002 and the DISCARD_SN 1004. The DISCARD_SN 1004 may include at least one sequence number of the at least one PDU.

[0135] In one aspect, multiple PDUs may be associated with an XR service. For example, multiple PDUs may be associated with Figure 4 The XR business shown in is associated with.

[0136] Fig.17 1700 is a flow chart of a method of wireless communication at a second wireless device. The method may be performed by an RLC transmitter (e.g., RLC transmitter 1404). The RLC transmitter may be a UE (e.g., UE 104, UE 350, apparatus 2304). The RLC transmitter may be a network entity (e.g., base station 102, CU 110, DU 130, RU 140, base station 310, network entity 2402). In an example, the method may be performed by PDU discard component 198 or PDU discard component 199. The method is associated with increased communication reliability of UE and / or network entity.

[0137] At 1702, a second wireless device communicates a plurality of PDUs associated with a DRB with a first wireless device. For example, Fig.14 At 1410, it is shown that the RLC transmitter 1404 can send a PDU to the RLC receiver 1402. In another example, multiple PDUs can be in the same Figure 5 1702 may be performed by the PDU discarding component 198 or the PDU discarding component 199, for example.

[0138] At 1704, the second wireless device receives a discard status report associated with at least one PDU of the plurality of PDUs that satisfies at least one discard criterion from the first wireless device. Fig.14 At 1418, the RLC transmitter 1404 may receive a discard status report. In an example, the discard status report may be received at Figure 8 , 9 , 10 and 11 respectively shown in the status report 800, the status report 900, the status report 1000 or the status report 1100. For example, 1704 can be performed by the PDU discarding component 198 or the PDU discarding component 199.

[0139] At 1706, the second wireless device updates the sliding window of the DRB based on the discard status report. For example, Fig.14 The RLC transmitter 1404 may advance the transmitter sliding window as shown at 1420. In another example, the RLC transmitter 704 may advance Figure 7 1706. For example, 1706 can be performed by PDU discard component 198 or PDU discard component 199. Updating the sliding window can avoid transmission stalls from the second wireless device to the first wireless device.

[0140] Fig.18 1800 is a flow chart of a method of wireless communication at a second wireless device. The method (including various aspects detailed below) may be performed by an RLC transmitter (e.g., RLC transmitter 1404). The RLC transmitter may be a UE (e.g., UE 104, UE 350, apparatus 2304). The RLC transmitter may be a network entity (e.g., base station 102, CU 110, DU 130, RU 140, base station 310, network entity 2402). In an example, the method (including various aspects detailed below) may be performed by PDU discard component 198 or PDU discard component 199. The method is associated with increased communication reliability of UEs and / or network entities.

[0141] At 1804, the second wireless device communicates a plurality of PDUs associated with the DRBs with the first wireless device. For example, Fig.14 At 1410, it is shown that the RLC transmitter 1404 can send a PDU to the RLC receiver 1402. In another example, multiple PDUs can be in the same Figure 5 1804 may be performed by the PDU discarding component 198 or the PDU discarding component 199, for example.

[0142] At 1806, the second wireless device receives a discard status report associated with at least one PDU in the plurality of PDUs that satisfies at least one discard criterion from the first wireless device. Fig.14 At 1418, the RLC transmitter 1404 may receive a discard status report. In an example, the discard status report may be received at Figure 8 , 9 , 10 and 11 respectively shown in the status report 800, the status report 900, the status report 1000 or the status report 1100. For example, 1806 can be performed by the PDU discarding component 198 or the PDU discarding component 199.

[0143] At 1808, the second wireless device updates the sliding window of the DRB based on the discard status report. For example, Fig.14 The RLC transmitter 1404 may advance the transmitter sliding window as shown at 1420. In another example, the RLC transmitter 704 may advance Figure 7 1808 can be performed by the PDU discarding component 198 or the PDU discarding component 199. Updating the sliding window can avoid transmission stalls from the second wireless device to the first wireless device.

[0144] In one aspect, the at least one discard criterion may include one or more of the following: intra-PDU set dependency, missed delay deadline, FEC decoding redundancy rate above a decoding threshold, or inter-frame dependency. Fig.14 The criteria shown at 1414 may include intra-PDU set dependency, missed delay deadline, FEC coding redundancy rate above a decoding threshold, and / or inter-frame dependency.

[0145] In one aspect, the DRB may be an AM DRB. For example, Figure 5 A DRB 514 is shown which may be an AM DRB.

[0146] In one aspect, at 1802, the second wireless device may send a configuration for a status prohibit timer associated with a lost PDU or a status report prohibit timer associated with a PDU discard, wherein the discard status report is associated with the status prohibit timer or the status report prohibit timer. Fig.14 At 1406, it is shown that the RLC transmitter 1404 can send a timer configuration. The timer configuration can be associated with a status prohibit timer or a status report prohibit timer. For example, 1802 can be performed by the PDU discard component 198 or the PDU discard component 199.

[0147] In one aspect, the discard status report may be received at a time corresponding to the expiration of a status prohibit timer or a status report prohibit timer. Fig.14 It is shown that the RLC transmitter 1404 can receive the discard status report according to the timer rules.

[0148] In one aspect, the discard status report may utilize an acknowledgment field to indicate at least one sequence number of at least one PDU. For example, the acknowledgment field may be Figure 8 and Fig. 9 ACK_SN 802 or ACK_SN 902 shown in FIG.

[0149] In one aspect, the discard status report may include at least one additional field compared to at least one other discard status report, wherein the at least one additional field includes at least one sequence number of the at least one PDU. For example, the at least one additional field may include the E4 field 1002 and the DISCARD_SN 1004. The DISCARD_SN 1004 may include at least one sequence number of the at least one PDU.

[0150] In one aspect, at 1810, the second wireless device may send an indication to the PDCP layer indicating that each RLC SDU in a set of RLC SDUs associated with at least one PDU has been discarded. Fig.14 At 1419, it is shown that the RLC transmitter 1404 can send an indication to one or more upper layers (e.g., a PDCP layer) indicating that the set of RLC SDUs has been discarded. In an example, the RLC SDU can be Figure 5 For example, 1810 may be performed by PDU discard component 198 or PDU discard component 199.

[0151] In one aspect, multiple PDUs may be associated with an XR service. For example, multiple PDUs may be associated with Figure 4 The XR business shown in is associated with.

[0152] In one aspect, at 1808A, the second wireless device may maintain an acknowledgment state variable and a transmission state variable, wherein a sequence number of an RLC SDU associated with at least one PDU associated with a discard status report is greater than or equal to a first value of the acknowledgment state variable and less than or equal to a second value of the transmission state variable, and updating a sliding window of a DRB based on the discard status report may include setting the first value of the acknowledgment state variable equal to the sequence number, wherein the RLC SDU belongs to a set of RLC SDUs for which the second wireless device has not received a positive acknowledgment, wherein the sequence number is less than each sequence number of the set of RLC SDUs. For example, in Fig.14 Advancing the transmitter sliding window shown at 1420 in may include setting the first value of the acknowledgement state variable equal to the sequence number as described above. For example, 1808A may be performed by PDU discard component 198 or PDU discard component 199.

[0153] Fig.19 1900 is a flow chart of a method of wireless communication at a first wireless device. The method may be performed by an RLC receiver (e.g., RLC receiver 1402). The RLC receiver may be a UE (e.g., UE 104, UE 350, apparatus 2304). The RLC receiver may be a network entity (e.g., base station 102, CU 110, DU 130, RU 140, base station 310, network entity 2402). In an example, the method may be performed by PDU discard component 198 or PDU discard component 199. The method is associated with increased communication reliability of UE and / or network entity.

[0154] At 1902, a first wireless device transmits a plurality of PDUs associated with a DRB with a second wireless device. For example, Fig.14 At 1410, it is shown that the RLC receiver 1402 can receive a PDU from the RLC transmitter 1404. In an example, the PDU can be Figure 5 1902 may be performed by the PDU discarding component 198 or the PDU discarding component 199, for example.

[0155] At 1904, the first wireless device receives an indication of a sequence number gap associated with at least one PDU in the plurality of PDUs from a second wireless device based on expiration of a PDCP discard timer. Fig.14 At 1430, it is shown that the RLC receiver 1402 may receive a discard indication control PDU including the SN of the discarded PDU. Fig.14It is also shown that the RLC receiver 1402 can receive a discard indication control PDU based on the expiration of the inhibit timer. In an example, the indication of the sequence number gap can be provided by Fig.12 The DISCARD_SN 1206 of the discard indication control PDU 1200 or Fig.13 In another example, the at least one PDU may be one of the RLC PDUs 502-506. Figure 6 An example of a gap is shown. For example, 1904 can be performed by PDU discard component 198 or PDU discard component 199.

[0156] At 1906, the first wireless device updates the sliding window of the DRB based on the sequence number gap. For example, Fig.14 At 1432, it is shown that the RLC receiver 1402 can advance the receiver sliding window based on the discard indication control PDU. In another example, Figure 6 The RLC receiver 604 in the embodiment may update the receiver side sliding window 606. For example, 1906 may be performed by the PDU discarding component 198 or the PDU discarding component 199. Updating the sliding window may cause the first wireless device to receive the communication in a faster manner because the first wireless device may not continue to wait to receive the PDU discarded by the second wireless device.

[0157] Fig. 20 2000 is a flow chart of a method of wireless communication at a first wireless device. The method (including various aspects detailed below) may be performed by an RLC receiver (e.g., RLC receiver 1402). The RLC receiver may be a UE (e.g., UE 104, UE 350, apparatus 2304). The RLC receiver may be a network entity (e.g., base station 102, CU 110, DU 130, RU 140, base station 310, network entity 2402). In an example, the method (including various aspects detailed below) may be performed by PDU discard component 198 or PDU discard component 199. The method is associated with increased communication reliability of UE and / or network entity.

[0158] At 2002, a first wireless device and a second wireless device transmit a plurality of PDUs associated with a DRB. For example, Fig.14 At 1410, it is shown that the RLC receiver 1402 can receive a PDU from the RLC transmitter 1404. In an example, the PDU can be Figure 5 2002 may be performed by the PDU discarding component 198 or the PDU discarding component 199, for example.

[0159] At 2004, the first wireless device receives an indication of a sequence number gap associated with at least one PDU in the plurality of PDUs from a second wireless device based on expiration of a PDCP discard timer. Fig.14 At 1430, it is shown that the RLC receiver 1402 may receive a discard indication control PDU including the SN of the discarded PDU. Fig.14 It is also shown that the RLC receiver 1402 can receive a discard indication control PDU based on the expiration of the inhibit timer. In an example, the indication of the sequence number gap can be provided by Fig.12 The DISCARD_SN 1206 of the discard indication control PDU 1200 or Fig.13 In another example, the at least one PDU may be one of the RLC PDUs 502-506. Figure 6 An example of a gap is shown. For example, 2004 can be performed by PDU discard component 198 or PDU discard component 199.

[0160] At 2006, the first wireless device updates the sliding window of the DRB based on the sequence number gap. For example, Fig.14 At 1432, it is shown that the RLC receiver 1402 can advance the receiver sliding window based on the discard indication control PDU. In another example, Figure 6 The RLC receiver 604 in the embodiment may update the receiver side sliding window 606. For example, 2006 may be performed by the PDU discarding component 198 or the PDU discarding component 199. Updating the sliding window may cause the first wireless device to receive the communication in a faster manner because the first wireless device may not continue to wait to receive the PDU discarded by the second wireless device.

[0161] In one aspect, the DRB may be an AM DRB. For example, Figure 5 A DRB 514 is shown which may be an AM DRB.

[0162] In one aspect, the indication of the sequence number gap may be included in a control PDU. For example, the control PDU may be a discard indication control PDU 1200 or a discard indication control PDU 1300. In an example, the indication of the sequence number gap may be respectively Fig.12 and Fig.13 The DISCARD_SN 1206 or DISCARD_SN 1306 is used to indicate this.

[0163] In one aspect, the control PDU may include: a first field indicating that the control PDU is used for control, a second field indicating that the control PDU includes a discard indication, a third field including an indication of a sequence number gap, and a fourth field further indicating a discard indication. For example, the first field may be the D / C field 1202, the second field may be the CPT field 1204, the third field may be the DISCARD_SN 1206, and the fourth field may be the E1 field 1210.

[0164] In one aspect, multiple PDUs may be associated with an XR service. For example, multiple PDUs may be associated with Figure 4 The XR business shown in is associated with.

[0165] In one aspect, at 2006A, the first wireless device may maintain a maximum state transmission variable and a reception state variable, and updating the sliding window of the DRB based on the sequence number gap may include: if the sequence number gap is equal to a first value of the maximum state transmission variable, the first wireless device updates the first value of the maximum state transmission variable to be equal to a sequence number of the RLC SDU for each byte of which it has not yet received, wherein the sequence number is greater than the first value. For example, referring to Fig.14 Advancing the receiver sliding window at 1432 may include updating a first value of a maximum state send variable equal to a sequence number of the RLC SDU for each byte of which has not been received. For example, 2006A may be performed by PDU discard component 198 or PDU discard component 199.

[0166] In one aspect, at 2006B, the first wireless device may maintain a maximum state transmission variable and a reception state variable, and updating the sliding window of the DRB based on the sequence number gap may include: if the sequence gap number is equal to a second value of the reception state variable, the first wireless device updates the second value of the reception state variable to be equal to a sequence number of the RLC SDU for each byte of which it has not yet received, wherein the sequence number is greater than the second value. For example, referring to Fig.14 Advancing the receiver sliding window at 1432 may include updating the second value of the receive state variable to be equal to the sequence number of the RLC SDU for each byte of which has not been received. For example, 2006B may be performed by PDU discard component 198 or PDU discard component 199.

[0167] Fig.212100 is a flow chart of a method of wireless communication at a second wireless device. The method may be performed by an RLC transmitter (e.g., RLC transmitter 1404). The RLC transmitter may be a UE (e.g., UE 104, UE 350, apparatus 2304). The RLC transmitter may be a network entity (e.g., base station 102, CU 110, DU 130, RU 140, base station 310, network entity 2402). In an example, the method may be performed by PDU discard component 198 or PDU discard component 199. The method is associated with increased communication reliability of UE and / or network entity.

[0168] At 2102, the second wireless device transmits a plurality of PDUs associated with the DRBs with the first wireless device. For example, Fig.14 At 1410, it is shown that the RLC transmitter 1404 can send a PDU to the RLC receiver 1402. In an example, the PDU can be related to Figure 5 2102 may be performed by the PDU discarding component 198 or the PDU discarding component 199, for example.

[0169] At 2104, the second wireless device detects expiration of a PDCP discard timer associated with at least one PDU of the plurality of PDUs. In an example, the at least one PDU may be one of the RLC PDUs 502-506. For example, Fig.14 The RLC transmitter 1404 can detect expiration of the inhibit timer, as shown at 1429. For example, 2104 can be performed by the PDU discard component 198 or the PDU discard component 199.

[0170] At 2106, the second wireless device sends an indication of a sequence number gap associated with at least one PDU in the plurality of PDUs to the first wireless device based on expiration of the PDCP discard timer. Fig.14 At 1430, the RLC transmitter 1404 may send a discard indication control PDU that may include the SN of the discarded PDU. In an example, the indication of the sequence number gap may be provided by Fig.12 The DISCARD_SN 1206 of the discard indication control PDU 1200 or Fig.13 In another example, the discard indication control PDU 1300 is indicated by DISCARD_SN 1306. Figure 6 An example of a gap is shown. For example, 2106 can be performed by PDU discard component 198 or PDU discard component 199.

[0171] Fig. 222200 is a flow chart of a method of wireless communication at a second wireless device. The method (including various aspects detailed below) may be performed by an RLC transmitter (e.g., RLC transmitter 1404). The RLC transmitter may be a UE (e.g., UE 104, UE 350, apparatus 2304). The RLC transmitter may be a network entity (e.g., base station 102, CU 110, DU 130, RU 140, base station 310, network entity 2402). In an example, the method (including various aspects detailed below) may be performed by PDU discard component 198 or PDU discard component 199. The method is associated with increased communication reliability of UEs and / or network entities.

[0172] At 2202, the second wireless device transmits a plurality of PDUs associated with the DRBs with the first wireless device. For example, Fig.14 At 1410, it is shown that the RLC transmitter 1404 can send a PDU to the RLC receiver 1402. In an example, the PDU can be related to Figure 5 2202 may be performed by the PDU discarding component 198 or the PDU discarding component 199, for example.

[0173] At 2204, the second wireless device detects expiration of a PDCP discard timer associated with at least one PDU of the plurality of PDUs. In an example, the at least one PDU may be one of the RLC PDUs 502-506. For example, Fig.14 The RLC transmitter 1404 can detect expiration of the inhibit timer, as shown at 1429. For example, 2204 can be performed by the PDU discard component 198 or the PDU discard component 199.

[0174] At 2206, the second wireless device sends an indication of a sequence number gap associated with at least one PDU in the plurality of PDUs to the first wireless device based on expiration of the PDCP discard timer. Fig.14 At 1430, the RLC transmitter 1404 may send a discard indication control PDU that may include the SN of the discarded PDU. In an example, the indication of the sequence number gap may be provided by Fig.12 The DISCARD_SN 1206 of the discard indication control PDU 1200 or Fig.13 In another example, the discard indication control PDU 1300 is indicated by DISCARD_SN 1306. Figure 6 An example of a gap is shown. For example, 2206 can be performed by PDU discard component 198 or PDU discard component 199.

[0175] In one aspect, the DRB may be an AM DRB. For example, Figure 5 A DRB 514 is shown which may be an AM DRB.

[0176] In one aspect, the indication of the sequence number gap may be included in a control PDU. For example, the control PDU may be a discard indication control PDU 1200 or a discard indication control PDU 1300. In an example, the indication of the sequence number gap may be respectively Fig.12 and Fig.13 The DISCARD_SN 1206 or DISCARD_SN 1306 is used to indicate this.

[0177] In one aspect, the control PDU may include: a first field indicating that the control PDU is used for control, a second field indicating that the control PDU includes a discard indication, a third field including an indication of a sequence number gap, and a fourth field further indicating a discard indication. For example, the first field may be the D / C field 1202, the second field may be the CPT field 1204, the third field may be the DISCARD_SN 1206, and the fourth field may be the E1 field 1210.

[0178] In one aspect, at 2208, the second wireless device may obtain a discard indication indicating that the at least one PDU is to be discarded. For example, Fig.14 The RLC transmitter 1404 can obtain a discard indication, as shown at 1426. For example, 2208 can be performed by PDU discard component 198 or PDU discard component 199.

[0179] In one aspect, at 2210, the second wireless device may discard at least one PDU based on the discard indication. For example, Fig.14 At 1428, it is shown that the RLC transmitter 1404 can discard the PDU based on the discard indication obtained at 1426. For example, 2210 can be performed by the PDU discard component 198 or the PDU discard component 199.

[0180] In one aspect, at 2210A, discarding the at least one PDU based on the discard indication may include discarding each RLC SDU in a set of RLC SDUs associated with the at least one PDU. For example, the set of RLC SDUs may be Figure 5 RLC SDUs 508-512 are shown. For example, 2210A can be performed by PDU discard component 198 or PDU discard component 199.

[0181] In one aspect, when a discard indication is obtained, a PDCP discard timer may be started. For example, Fig.14It is shown that when the RLC transmitter 1404 obtains a discard indication at 1426, the inhibit timer may begin running.

[0182] In one aspect, the plurality of PDUs are associated with XR services. For example, the plurality of PDUs may be associated with Figure 4 The XR business shown in is associated with.

[0183] Fig.232300 is a diagram illustrating an example of a hardware implementation for an apparatus 2304. The apparatus 2304 may be a UE, a component of a UE, or may implement UE functionality. In some aspects, the apparatus 2304 may include a cellular baseband processor 2324 (also referred to as a modem) coupled to one or more transceivers 2322 (e.g., a cellular RF transceiver). The cellular baseband processor 2324 may include on-chip memory 2324'. In some aspects, the apparatus 2304 may further include one or more subscriber identity module (SIM) cards 2320 and an application processor 2306 coupled to a secure digital (SD) card 2308 and a screen 2310. The application processor 2306 may include on-chip memory 2306'. In some aspects, the device 2304 may further include a Bluetooth module 2312, a WLAN module 2314, an SPS module 2316 (e.g., a GNSS module), one or more sensor modules 2318 (e.g., a barometric pressure sensor / altimeter; a motion sensor such as an inertial measurement unit (IMU), a gyroscope, and / or an accelerometer; light detection and ranging (LIDAR), radio-aided detection and ranging (RADAR), sound navigation and ranging (SONAR), a magnetometer, audio, and / or other technologies for positioning), an additional memory module 2326, a power source 2330, and / or a camera 2332. The Bluetooth module 2312, the WLAN module 2314, and the SPS module 2316 may include an on-chip transceiver (TRX) (or in some cases, only a receiver (RX)). The Bluetooth module 2312, the WLAN module 2314, and the SPS module 2316 may include their own dedicated antennas and / or communicate using antennas 2380. The cellular baseband processor 2324 communicates with the UE 104 and / or with the RU associated with the network entity 2302 via one or more antennas 2380 through the transceiver 2322. The cellular baseband processor 2324 and the application processor 2306 can each include a computer-readable medium / memory 2324', 2306', respectively. The additional memory module 2326 can also be considered as a computer-readable medium / memory. Each computer-readable medium / memory 2324', 2306', 2326 can be non-temporary. The cellular baseband processor 2324 and the application processor 2306 are each responsible for general processing, including executing software stored on the computer-readable medium / memory. When executed by the cellular baseband processor 2324 / application processor 2306, the software enables the cellular baseband processor 2324 / application processor 2306 to perform the various functions described above. The computer-readable medium / memory can also be used to store data manipulated by the cellular baseband processor 2324 / application processor 2306 when executing the software.The cellular baseband processor 2324 / application processor 2306 may be a component of the UE 350 and may include the memory 360 and / or at least one of the TX processor 368, the RX processor 356, and the controller / processor 359. In one configuration, the device 2304 may be a processor chip (modem and / or application) and include only the cellular baseband processor 2324 / application processor 2306, while in another configuration, the device 2304 may be the entire UE (e.g., see. Figure 3 350) and includes additional modules of device 2304.

[0184] As described above, the PDU discard component 198 is configured to transmit a plurality of PDUs associated with the DRB with the second wireless device. The PDU discard component 198 is configured to detect that at least one of the plurality of PDUs associated with the DRB satisfies at least one discard criterion. The PDU discard component 198 is configured to send a discard status report associated with at least one PDU that satisfies at least one discard criterion to the second wireless device. The PDU discard component 198 is configured to transmit a plurality of PDUs associated with the DRB with the first wireless device. The PDU discard component 198 is configured to receive a discard status report associated with at least one PDU that satisfies at least one discard criterion in the plurality of PDUs from the first wireless device. The PDU discard component 198 is configured to update a sliding window of the DRB based on the discard status report. The PDU discard component 198 is configured to transmit a plurality of PDUs associated with the DRB with the second wireless device. The PDU discard component 198 is configured to receive an indication of a sequence number gap associated with at least one PDU in the plurality of PDUs from the second wireless device based on expiration of a PDCP discard timer. The PDU discard component 198 is configured to update the sliding window of the DRB based on the sequence number gap. The PDU discard component 198 is configured to transmit a plurality of PDUs associated with the DRB to the first wireless device. The PDU discard component 198 is configured to detect the expiration of a PDCP discard timer associated with at least one of the plurality of PDUs. The PDU discard component 198 is configured to send an indication of a sequence number gap associated with at least one of the plurality of PDUs to the first wireless device based on the expiration of the PDCP discard timer. The PDU discard component 198 may be within the cellular baseband processor 2324, the application processor 2306, or within both the cellular baseband processor 2324 and the application processor 2306. The PDU discard component 198 may be one or more hardware components specifically configured to perform the process / algorithm, implemented by one or more processors configured to perform the process / algorithm, stored in a computer-readable medium for implementation by one or more processors, or some combination thereof. As shown, the apparatus 2304 may include various components configured for various functions. In one configuration, the apparatus 2304 (and in particular the cellular baseband processor 2324 and / or the application processor 2306) includes: a unit for transmitting a plurality of PDUs associated with the DRB to the second wireless device. In one configuration, the apparatus 2304 (and in particular the cellular baseband processor 2324 and / or the application processor 2306) includes: a unit for detecting that at least one PDU of the plurality of PDUs associated with the DRB satisfies at least one discard criterion.In one configuration, the apparatus 2304 (and specifically the cellular baseband processor 2324 and / or the application processor 2306) includes: a unit for sending a discard status report associated with at least one PDU that satisfies at least one discard criterion for a second wireless device. In one configuration, the apparatus 2304 (and specifically the cellular baseband processor 2324 and / or the application processor 2306) includes: a unit for discarding the at least one PDU upon detecting that the at least one PDU satisfies at least one discard criterion. In one configuration, the unit for discarding the at least one DU upon detecting that the at least one PDU satisfies at least one discard criterion includes: a unit for discarding each RLC SDU in a set of RLC SDUs associated with the at least one PDU. In one configuration, the apparatus 2304 (and specifically the cellular baseband processor 2324 and / or the application processor 2306) includes: a unit for receiving a configuration for a status prohibit timer associated with a lost PDU or a status report prohibit timer associated with a PDU discard, wherein the discard status report is associated with the status prohibit timer or the status report prohibit timer. In one configuration, the apparatus 2304 (and specifically the cellular baseband processor 2324 and / or the application processor 2306) includes: a unit for transmitting a plurality of PDUs associated with a DRB to a first wireless device. In one configuration, the apparatus 2304 (and specifically the cellular baseband processor 2324 and / or the application processor 2306) includes: a unit for receiving a discard status report associated with at least one PDU in the plurality of PDUs that satisfies at least one discard criterion from a second wireless device. In one configuration, the apparatus 2304 (and specifically the cellular baseband processor 2324 and / or the application processor 2306) includes: a unit for updating a sliding window of the DRB based on the discard status report. In one configuration, the apparatus 2304 (and specifically the cellular baseband processor 2324 and / or the application processor 2306) includes: a unit for sending a configuration for a status prohibit timer associated with a lost PDU or a status report prohibit timer associated with a PDU discard, wherein the discard status report is associated with the status prohibit timer or the status report prohibit timer. In one configuration, the apparatus 2304 (and specifically the cellular baseband processor 2324 and / or the application processor 2306) includes: a unit for sending an indication to the PDCP layer indicating that each RLC SDU in a set of RLC SDUs associated with at least one PDU has been discarded.In one configuration in which the second wireless device maintains an acknowledgment state variable and a transmission state variable, wherein a sequence number of an RLC SDU associated with at least one PDU associated with a discard status report is greater than or equal to a first value of the acknowledgment state variable and less than or equal to a second value of the transmission state variable, means for updating a sliding window of a DRB based on the discard status report comprises means for setting the first value of the acknowledgment state variable equal to the sequence number, wherein the RLC SDU belongs to a set of RLC SDUs for which the second wireless device has not received a positive acknowledgment, wherein the sequence number is less than each sequence number of the set of RLC SDUs. In one configuration, the apparatus 2304 (and in particular the cellular baseband processor 2324 and / or the application processor 2306) comprises means for transmitting a plurality of PDUs associated with the DRB to the second wireless device. In one configuration, the apparatus 2304 (and in particular the cellular baseband processor 2324 and / or the application processor 2306) comprises means for receiving, from the second wireless device, an indication of a sequence number gap associated with at least one PDU of the plurality of PDUs based on expiration of a PDCP discard timer. In one configuration, the apparatus 2304 (and specifically the cellular baseband processor 2324 and / or the application processor 2306) includes means for updating a sliding window of DRBs based on a sequence number gap. In a configuration in which the first wireless device maintains a maximum state transmit variable and a receive state variable, the means for updating a sliding window of DRBs based on a sequence number gap includes means for updating a first value of the maximum state transmit variable to be equal to a sequence number of an RLC SDU for each byte of which it has not yet received if the sequence number gap is equal to a first value of the maximum state transmit variable, wherein the sequence number is greater than the first value. In a configuration in which the first wireless device maintains a maximum state transmit variable and a receive state variable, the means for updating a sliding window of DRBs based on a sequence number gap may include means for updating a second value of the receive state variable to be equal to a sequence number of an RLC SDU for each byte of which it has not yet received if the sequence number gap is equal to a second value of the receive state variable, wherein the sequence number is greater than the second value. In one configuration, the apparatus 2304 (and in particular the cellular baseband processor 2324 and / or the application processor 2306) includes: means for transmitting a plurality of PDUs associated with the DRB to the first wireless device. In one configuration, the apparatus 2304 (and in particular the cellular baseband processor 2324 and / or the application processor 2306) includes: means for detecting expiration of a PDCP discard timer associated with at least one PDU of the plurality of PDUs.In one configuration, the apparatus 2304 (and specifically the cellular baseband processor 2324 and / or the application processor 2306) includes: a unit for sending an indication of a sequence number gap associated with at least one PDU in a plurality of PDUs to a first wireless device based on expiration of a PDCP discard timer. In one configuration, the apparatus 2304 (and specifically the cellular baseband processor 2324 and / or the application processor 2306) includes: a unit for obtaining a discard indication indicating that at least one PDU is to be discarded. In one configuration, the apparatus 2304 (and specifically the cellular baseband processor 2324 and / or the application processor 2306) includes: a unit for discarding at least one PDU based on the discard indication. In one configuration, the unit for discarding the at least one PDU based on the discard indication includes: a unit for discarding each RLC SDU in a set of RLC SDUs associated with the at least one PDU. The unit may be the PDU discard component 198 of the apparatus 2304, which is configured to perform the functions recited by the unit. As described above, the apparatus 2304 may include the TX processor 368, the RX processor 356, and the controller / processor 359. Thus, in one configuration, the means may be the TX processor 368, the RX processor 356, and the controller / processor 359 configured to perform the functions recited by the means.

[0185] Fig.242400 is a diagram illustrating an example of a hardware implementation for a network entity 2402. The network entity 2402 may be a BS, a component of a BS, or may implement BS functionality. The network entity 2402 may include at least one of a CU 2410, a DU 2430, or a RU 2440. For example, depending on the layer functionality handled by the PDU discard component 199, the network entity 2402 may include a CU 2410; both a CU 2410 and a DU 2430; each of the CU 2410, the DU 2430, and the RU 2440; the DU 2430; both a DU 2430 and a RU 2440; or a RU 2440. The CU 2410 may include a CU processor 2412. The CU processor 2412 may include an on-chip memory 2412'. In some aspects, the CU 2410 may further include an additional memory module 2414 and a communication interface 2418. CU 2410 communicates with DU 2430 via a mid-haul link such as an F1 interface. DU 2430 may include a DU processor 2432. DU processor 2432 may include on-chip memory 2432'. In some aspects, DU 2430 may further include an additional memory module 2434 and a communication interface 2438. DU 2430 communicates with RU 2440 via a front-haul link. RU 2440 may include a RU processor 2442. RU processor 2442 may include on-chip memory 2442'. In some aspects, RU 2440 may further include an additional memory module 2444, one or more transceivers 2446, an antenna 2480, and a communication interface 2448. RU 2440 communicates with UE 104. On-chip memory 2412', 2432', 2442' and additional memory modules 2414, 2434, 2444 can each be considered as a computer-readable medium / memory. Each computer-readable medium / memory can be non-temporary. Each of processors 2412, 2432, 2442 is responsible for general processing, which includes executing software stored on computer-readable medium / memory. The software, when executed by the corresponding processor, causes the processor to perform the various functions described above. The computer-readable medium / memory can also be used to store data manipulated by the processor when executing the software.

[0186] As described above, the PDU discard component 199 is configured to transmit a plurality of PDUs associated with the DRB with the second wireless device. The PDU discard component 199 is configured to detect that at least one of the plurality of PDUs associated with the DRB satisfies at least one discard criterion. The PDU discard component 199 is configured to send a discard status report associated with at least one PDU that satisfies at least one discard criterion to the second wireless device. The PDU discard component 199 is configured to transmit a plurality of PDUs associated with the DRB with the first wireless device. The PDU discard component 199 is configured to receive a discard status report associated with at least one PDU that satisfies at least one discard criterion in the plurality of PDUs from the first wireless device. The PDU discard component 199 is configured to update a sliding window of the DRB based on the discard status report. The PDU discard component 199 is configured to transmit a plurality of PDUs associated with the DRB with the second wireless device. The PDU discard component 199 is configured to receive an indication of a sequence number gap associated with at least one PDU in the plurality of PDUs from the second wireless device based on expiration of a PDCP discard timer. The PDU discard component 199 is configured to update the sliding window of the DRB based on the sequence number gap. The PDU discard component 199 is configured to transmit a plurality of PDUs associated with the DRB with the first wireless device. The PDU discard component 199 is configured to detect the expiration of a PDCP discard timer associated with at least one of the plurality of PDUs. The PDU discard component 199 is configured to send an indication of a sequence number gap associated with at least one of the plurality of PDUs to the first wireless device based on the expiration of the PDCP discard timer. The PDU discard component 199 may be within one or more processors of one or more of the CU 2410, the DU 2430, and the RU 2440. The PDU discard component 199 may be one or more hardware components specifically configured to execute the process / algorithm, implemented by one or more processors configured to execute the process / algorithm, stored in a computer-readable medium for implementation by one or more processors, or some combination thereof. The network entity 2402 may include various components configured for various functions. In one configuration, the network entity 2402 includes means for transmitting a plurality of PDUs associated with the DRB to a second wireless device. In one configuration, the network entity 2402 includes means for detecting that at least one of the plurality of PDUs associated with the DRB satisfies at least one discard criterion. In one configuration, the network entity 2402 includes means for sending a discard status report associated with at least one PDU satisfying at least one discard criterion to the second wireless device. In one configuration, the network entity 2402 includes means for discarding at least one PDU upon detecting that the at least one PDU satisfies at least one discard criterion.In one configuration, the network entity 2402 includes: a unit for discarding at least one PDU upon detecting that the at least one PDU satisfies at least one discard criterion, including: a unit for discarding each RLC SDU in a set of RLC SDUs associated with the at least one PDU. In one configuration, the network entity 2402 includes: a unit for receiving a configuration for a status prohibit timer associated with a lost PDU or a status report prohibit timer associated with a PDU discard, wherein the discard status report is associated with the status prohibit timer or the status report prohibit timer. In one configuration, the network entity 2402 includes: a unit for transmitting a plurality of PDUs associated with a DRB to a first wireless device. In one configuration, the network entity 2402 includes: a unit for receiving a discard status report associated with at least one PDU in the plurality of PDUs that satisfies at least one discard criterion from the first wireless device. In one configuration, the network entity 2402 includes: a unit for updating a sliding window of the DRB based on the discard status report. In one configuration, the network entity 2402 includes: means for sending a configuration for a status inhibit timer associated with a lost PDU or a status report inhibit timer associated with a PDU discard, wherein the discard status report is associated with the status inhibit timer or the status report inhibit timer. In one configuration, the network entity 2402 includes means for sending an indication to the PDCP layer indicating that each RLC SDU in a set of RLC SDUs associated with the at least one PDU has been discarded. In one configuration in which the second wireless device maintains an acknowledgment state variable and a transmission state variable, wherein a sequence number of the RLC SDU associated with the at least one PDU associated with the discard status report is greater than or equal to a first value of the acknowledgment state variable and less than or equal to a second value of the transmission state variable, the means for updating a sliding window of a DRB based on the discard status report includes: means for setting the first value of the acknowledgment state variable equal to the sequence number, wherein the RLC SDU belongs to a set of RLC SDUs for which the second wireless device has not received a positive acknowledgment, wherein the sequence number is less than each sequence number of the set of RLC SDUs. In one configuration, the network entity 2402 includes means for transmitting a plurality of PDUs associated with the DRB with the second wireless device. In one configuration, the network entity 2402 includes means for receiving, from the second wireless device, an indication of a sequence number gap associated with at least one PDU in the plurality of PDUs based on expiration of a PDCP discard timer. In one configuration, the network entity 2402 includes means for updating a sliding window of the DRB based on the sequence number gap.In a configuration in which the first wireless device maintains a maximum state send variable and a receive state variable, the means for updating the sliding window of the DRB based on the sequence number gap includes: means for updating the first value of the maximum state send variable to be equal to the sequence number of the RLC SDU for each byte of which it has not received if the sequence number gap is equal to a first value of the maximum state send variable, wherein the sequence number is greater than the first value. In a configuration in which the first wireless device maintains a maximum state send variable and a receive state variable, the means for updating the sliding window of the DRB based on the sequence number gap may include: means for updating the second value of the receive state variable to be equal to the sequence number of the RLC SDU for each byte of which it has not received if the sequence gap number is equal to a second value of the receive state variable, wherein the sequence number is greater than the second value. In one configuration, the network entity 2402 includes: means for transmitting a plurality of PDUs associated with the DRB with the first wireless device. In one configuration, the network entity 2402 includes: means for detecting expiration of a PDCP discard timer associated with at least one of the plurality of PDUs. In one configuration, the network entity 2402 includes: a unit for sending an indication of a sequence number gap associated with at least one PDU in a plurality of PDUs to a first wireless device based on expiration of a PDCP discard timer. In one configuration, the network entity 2402 includes: a unit for obtaining a discard indication indicating that at least one PDU is to be discarded. In one configuration, the network entity 2402 includes: a unit for discarding at least one PDU based on the discard indication. In one configuration, the unit for discarding the at least one PDU based on the discard indication includes: a unit for discarding each RLC SDU in a set of RLC SDUs associated with the at least one PDU. The unit may be a PDU discard component 199 of the network entity 2402, the PDU discard component being configured to perform the functions recited by the unit. As described above, the network entity 2402 may include at least one of a TX processor 316, an RX processor 370, and / or a controller / processor 375. Thus, in one configuration, the means may be the TX processor 316, the RX processor 370, and the controller / processor 375 configured to perform the functions recited by the means.

[0187] In the layer 2 (L2) process, various types of events can trigger PDU discarding. For example, if a PDU misses a configured delay budget or a signaled delivery deadline, the PDU may become obsolete. PDU discarding can be triggered by intra-PDU set dependency. In one example, a PDU set can be configured so that each PDU in the PDU set will be sent or received. If a PDU in a PDU set is discarded, other PDUs in the PDU set may also be discarded. In another example, if a PDU in a PDU set is discarded, subsequent PDUs in the PDU set may also be discarded. PDU discarding can also be triggered by inter-frame dependencies. In an example, there may be dependencies between PDUs in a quality of service (QoS) stream. For example, a predicted picture frame (p frame) in a decoded video stream may depend on an intra-frame decoded picture frame (I frame) in the same burst. If the UE discards an I frame, the UE may also discard the associated P frame because such a frame may be obsolete. If the RLC receiver discards the PDU but does not notify the RLC transmitter of the discard, the RLC transmitter may not advance the transmitter-side automatic repeat request (ARQ) window. This may delay further transmissions by the RLC transmitter. If the RLC transmitter discards the PDU but does not notify the RLC receiver of the discard, there may be gaps in the RLC PDU SNs. This may delay the advancement of the receiver-side ARQ window.

[0188] Various techniques related to PDU discard are described herein. In an example, a first wireless device transmits a plurality of PDUs associated with a DRB with a second wireless device. The first wireless device detects that at least one of the plurality of PDUs associated with the DRB satisfies at least one discard criterion. The first wireless device sends a discard status report associated with at least one PDU that satisfies at least one discard criterion to the second wireless device. The second wireless device may update a sliding window based on the discard status report. Thus, the discard status report may prevent transmission stagnation of the second wireless device, and thus may result in increased communication reliability at the first wireless device. In another example, a first wireless device transmits a plurality of PDUs associated with a DRB with a second wireless device. The first wireless device receives an indication of a sequence number gap associated with at least one of the plurality of PDUs from the second wireless device based on expiration of a PDCP discard timer. The first wireless device updates a sliding window of the DRB based on the sequence number gap. Thus, the indication of the sequence number gap may help the first wireless device update the sliding window, and may result in increased communication reliability at the first wireless device.

[0189] It should be understood that the specific order or hierarchy of the blocks in the disclosed process / flowchart is only an illustration of the exemplary method. It should be understood that the specific order or hierarchy of the blocks in the process / flowchart can be rearranged based on design preferences. Further, some blocks can be combined or omitted. The attached method claims provide the elements of each block in a sample order, but are not limited to the specific order or hierarchy provided.

[0190] The foregoing description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects. Therefore, the claims are not limited to the aspects described herein, but are to be given the full scope consistent with the claim expressions. Unless otherwise specifically stated, reference to elements in the singular form is not intended to mean "one and only one", but "one or more". Terms such as "if", "when" and "at..." do not imply a direct temporal relationship or reaction. That is, these phrases, such as "when", do not imply a direct action in response to the occurrence of an action or during the occurrence of an action, but simply imply that if the conditions are met, then the action will occur, but no specific or immediate time limit is required for the action to occur. The word "exemplary" used herein means "as an example, instance or illustration". Any aspect described as "exemplary" herein is not necessarily interpreted as being preferred or having advantages over other aspects. Unless otherwise specifically stated, the term "some" refers to one or more. Combinations such as "at least one of A, B, or C", "one or more of A, B, or C", "at least one of A, B and C", "one or more of A, B, and C", and "A, B, C, or any combination thereof" include any combination of A, B, and / or C, and may include multiples of A, multiples of B, or multiples of C. Specifically, combinations such as "at least one of A, B, or C", "one or more of A, B, or C", "at least one of A, B, and C", "one or more of A and B", and "A, B, C, or any combination thereof" may be only A, only B, only C, A and B, A and C, B and C, or A and B and C, wherein any such combination may contain one or more members of A, B, or C, and a set should be interpreted as a set of elements whose element number is one or more. Thus, for a set of X, X will include one or more elements. If a first device receives data from or sends data to a second device, the data may be received / sent directly between the first device and the second device, or the data may be received / sent indirectly between the first device and the second device through a set of devices. All structural and functional equivalents of the elements of the various aspects described throughout the present disclosure that are known or will later be known to those of ordinary skill in the art are expressly incorporated herein by reference and are covered by the claims. In addition, nothing disclosed herein is dedicated to the public, regardless of whether such disclosure is explicitly recorded in the claims. Words such as "module", "mechanism", "element", "device" are not substitutes for the word "unit". As such, no claim element is to be interpreted as a functional unit unless the element is explicitly recorded using the phrase "unit for..."

[0191] As used herein, the phrase "based on" should not be interpreted as a reference to a closed set of information, one or more conditions, one or more factors, etc. In other words, the phrase "based on A" (where "A" can be information, conditions, factors, etc.) should be interpreted as "based at least on A" unless specifically stated differently.

[0192] The following aspects are merely illustrative and may be combined with other aspects or teachings described herein without limitation.

[0193] Aspect 1 is a method of wireless communication at a first wireless device, comprising: transmitting multiple PDUs associated with a DRB to a second wireless device; detecting that at least one PDU among the multiple PDUs associated with the DRB satisfies at least one discard criterion; and sending a discard status report associated with the at least one PDU that satisfies the at least one discard criterion to the second wireless device.

[0194] Aspect 2 is a method according to aspect 1, wherein the at least one discarding criterion includes one or more of the following: intra-PDU set dependency, missed delay deadline, FEC decoding redundancy rate higher than a decoding threshold, or inter-frame dependency.

[0195] Aspect 3 is a method according to any one of aspects 1-2, further comprising: discarding the at least one PDU upon detecting that the at least one PDU satisfies at least one discard criterion.

[0196] Aspect 4 is a method according to aspect 3, wherein discarding at least one PDU includes discarding each RLC SDU in a set of RLC SDUs associated with the at least one PDU.

[0197] Aspect 5 is a method according to any one of aspects 1-4, wherein the DRB is an AM DRB.

[0198] Aspect 6 is a method according to any one of Aspects 1-5, further comprising: receiving a configuration for a status prohibit timer associated with a lost PDU or a status report prohibit timer associated with a PDU discard, wherein the discard status report is associated with the status prohibit timer or the status report prohibit timer.

[0199] Aspect 7 is the method according to aspect 6, wherein the discard status report is sent at a time corresponding to expiration of a status prohibit timer or a status report prohibit timer.

[0200] Aspect 8 is a method according to any one of aspects 1-7, wherein the discard status report utilizes an acknowledgment field to indicate at least one sequence number of at least one PDU.

[0201] Aspect 9 is a method according to any one of aspects 1-8, wherein the discard status report includes at least one additional field compared to at least one other discard status report, wherein the at least one additional field includes at least one sequence number of the at least one PDU.

[0202] Aspect 10 is a method according to any one of aspects 1-9, wherein a plurality of PDUs are associated with XR services.

[0203] Aspect 11 is an apparatus for wireless communication at a first wireless device, comprising a memory and at least one processor coupled to the memory, and based at least in part on information stored in the memory, the at least one processor is configured to perform a method according to any one of aspects 1-10.

[0204] Aspect 12 is an apparatus for wireless communication, comprising means for executing the method according to any one of aspects 1-10.

[0205] Aspect 13 is an apparatus according to Aspect 11 or 12, further comprising at least one of a transceiver or an antenna coupled to the at least one processor, wherein the at least one processor is configured to send the discard status report via at least one of the transceiver or the antenna.

[0206] Aspect 14 is a non-transitory computer-readable medium comprising instructions which, when executed by an apparatus, cause the apparatus to perform the method according to any one of aspects 1-10.

[0207] Aspect 15 is a method of wireless communication at a second wireless device, comprising: transmitting multiple PDUs associated with a DRB to a first wireless device; receiving a discard status report associated with at least one PDU among the multiple PDUs that meets at least one discard criterion from the first wireless device; and updating a sliding window of the DRB based on the discard status report.

[0208] Aspect 16 is a method according to aspect 15, wherein the at least one discarding criterion includes one or more of the following: intra-PDU set dependency, missed delay deadline, FEC decoding redundancy rate above decoding threshold, or inter-frame dependency.

[0209] Aspect 17 is a method according to any one of aspects 15-16, wherein the DRB is an AM DRB.

[0210] Aspect 18 is a method according to any one of Aspects 15-17, further comprising: sending a configuration for a status prohibit timer associated with a lost PDU or a status report prohibit timer associated with a PDU discard, wherein the discard status report is associated with the status prohibit timer or the status report prohibit timer.

[0211] Aspect 19 is a method according to aspect 18, wherein the discard status report is received at a time corresponding to expiration of a status prohibit timer or a status report prohibit timer.

[0212] Aspect 20 is a method according to any one of aspects 15-19, wherein the discard status report utilizes an acknowledgment field to indicate at least one sequence number of at least one PDU.

[0213] Aspect 21 is a method according to any one of aspects 15-20, wherein the discard status report includes at least one additional field compared to at least one other discard status report, wherein the at least one additional field includes at least one sequence number of the at least one PDU.

[0214] Aspect 22 is a method according to aspect 21, further comprising: sending an indication to the PDCP layer indicating that each RLC SDU in the set of RLC SDUs associated with the at least one PDU has been discarded.

[0215] Aspect 23 is a method according to any one of aspects 15-22, wherein the plurality of PDUs are associated with XR services.

[0216] Aspect 24 is a method according to any one of Aspects 15-23, wherein the second wireless device maintains a confirmation state variable and a sending state variable, wherein the sequence number of the RLC SDU associated with at least one PDU associated with the discard status report is greater than or equal to the first value of the confirmation state variable and less than or equal to the second value of the sending state variable, wherein updating the sliding window of the DRB based on the discard status report includes: setting the first value of the confirmation state variable equal to the sequence number, wherein the RLC SDU belongs to a set of RLC SDUs for which the second wireless device has not yet received a positive confirmation, and wherein the sequence number is less than each sequence number of the set of RLC SDUs.

[0217] Aspect 25 is an apparatus for wireless communication at a second wireless device, comprising a memory and at least one processor coupled to the memory, and based at least in part on information stored in the memory, the at least one processor is configured to perform a method according to any one of aspects 15-24.

[0218] Aspect 26 is an apparatus for wireless communication, comprising means for performing the method as described in any one of aspects 15-24.

[0219] Aspect 27 is an apparatus according to Aspect 25 or 26, further comprising at least one of a transceiver or an antenna coupled to the at least one processor, wherein the at least one processor is configured to receive the discard status report via at least one of the transceiver or the antenna.

[0220] Aspect 28 is a non-transitory computer-readable medium comprising instructions which, when executed by an apparatus, cause the apparatus to perform the method according to any one of aspects 15-24.

[0221] Aspect 29 is a method of wireless communication at a first wireless device, comprising: transmitting multiple PDUs associated with a DRB to a second wireless device; based on expiration of a PDCP discard timer, receiving an indication of a sequence number gap associated with at least one PDU in the multiple PDUs from the second wireless device; and updating a sliding window of the DRB based on the sequence number gap.

[0222] Aspect 30 is a method according to aspect 29, wherein the DRB is an AM DRB.

[0223] Aspect 31 is a method according to any one of aspects 29-30, wherein the indication of the sequence number gap is included in the control PDU.

[0224] Aspect 32 is a method according to aspect 31, wherein the control PDU includes: a first field indicating that the control PDU is used for control, a second field indicating that the control PDU includes a discard indication, a third field including an indication of a sequence number gap, and a fourth field also indicating a discard indication.

[0225] Aspect 33 is a method according to any one of aspects 29-32, wherein the plurality of PDUs are associated with the XR service.

[0226] Aspect 34 is a method according to any one of Aspects 29-33, wherein the first wireless device maintains a maximum state transmission variable and a reception state variable, and wherein updating the sliding window of the DRB based on the sequence number gap includes: if the sequence number gap is equal to a first value of the maximum state transmission variable, then updating the first value of the maximum state transmission variable to be equal to the sequence number of the RLC SDU for each byte that has not been received, wherein the sequence number is greater than the first value; or, if the sequence gap number is equal to a second value of the reception state variable, then updating the second value of the reception state variable to be equal to the sequence number of the RLC SDU for each byte that has not been received, wherein the sequence number is greater than the second value.

[0227] Aspect 35 is an apparatus for wireless communication at a first wireless device, comprising a memory and at least one processor coupled to the memory, and based at least in part on information stored in the memory, the at least one processor is configured to perform a method according to any one of aspects 29-34.

[0228] Aspect 36 is an apparatus for wireless communication, comprising means for performing the method as described in any one of aspects 29-34.

[0229] Aspect 37 is an apparatus according to Aspect 35 or 36, further comprising at least one of a transceiver or an antenna coupled to the at least one processor, wherein the at least one processor is configured to receive an indication of a sequence number gap via at least one of the transceiver or the antenna.

[0230] Aspect 38 is a non-transitory computer-readable medium comprising instructions which, when executed by an apparatus, cause the apparatus to perform a method according to any one of aspects 29-34.

[0231] Aspect 39 is a method of wireless communication at a second wireless device, comprising: transmitting multiple PDUs associated with DRBs to a first wireless device; detecting expiration of a PDCP discard timer associated with at least one PDU among the multiple PDUs; and sending an indication of a sequence number gap associated with at least one PDU among the multiple PDUs to the first wireless device based on the expiration of the PDCP discard timer.

[0232] Aspect 40 is a method according to aspect 39, wherein the DRB is an AM DRB.

[0233] Aspect 41 is a method according to any one of aspects 39-40, wherein the indication of the sequence number gap is included in the control PDU.

[0234] Aspect 42 is a method according to aspect 41, wherein the control PDU includes: a first field indicating that the control PDU is used for control, a second field indicating that the control PDU includes a discard indication, a third field including an indication of a sequence number gap, and a fourth field also indicating a discard indication.

[0235] Aspect 43 is a method according to any one of aspects 39-42, further comprising: obtaining a discard indication indicating that the at least one PDU is to be discarded; and discarding the at least one PDU based on the discard indication.

[0236] Aspect 44 is a method according to aspect 43, wherein discarding at least one PDU based on the discard indication includes discarding each RLC SDU in a set of RLC SDUs associated with the at least one PDU.

[0237] Aspect 45 is a method according to aspect 43, wherein a PDCP discard timer is started when a discard indication is obtained.

[0238] Aspect 46 is a method according to any one of aspects 39-45, wherein a plurality of PDUs are associated with XR services.

[0239] Aspect 47 is an apparatus for wireless communication at a second wireless device, comprising a memory and at least one processor coupled to the memory, and based at least in part on information stored in the memory, the at least one processor is configured to perform a method according to any one of Aspects 39-46.

[0240] Aspect 48 is an apparatus for wireless communication, comprising means for performing the method as described in any of aspects 39-46.

[0241] Aspect 49 is an apparatus according to Aspect 47 or 48, further comprising at least one of a transceiver or an antenna coupled to the at least one processor, wherein the at least one processor is configured to send an indication of a sequence number gap via at least one of the transceiver or the antenna.

[0242] Aspect 50 is a non-transitory computer-readable medium comprising instructions which, when executed by an apparatus, cause the apparatus to perform a method according to any one of aspects 39-46.

Claims

1. An apparatus for wireless communication at a first wireless device, comprising: Memory; as well as at least one processor coupled to the memory and based at least in part on the information stored in the memory, the at least one processor is configured to: communicating, with a second wireless device, a plurality of protocol data units (PDUs) associated with a data radio bearer (DRB); detecting that at least one PDU of the plurality of PDUs associated with the DRB satisfies at least one discard criterion; as well as A discard status report associated with the at least one PDU satisfying the at least one discard criterion is sent to the second wireless device.

2. The device according to claim 1, wherein: The at least one discard criterion includes one or more of: intra-PDU set dependency, missed delay deadline, stream error correction (FEC) decoding redundancy rate above a decoding threshold, or inter-frame dependency.

3. The device according to claim 1, wherein: The at least one processor is further configured to: The at least one PDU is discarded upon detecting that the at least one PDU satisfies the at least one discard criterion.

4. The device according to claim 3, wherein: To discard the at least one PDU, the at least one processor is further configured to: Each radio link control (RLC) service data unit (SDU) in a set of RLC SDUs associated with the at least one PDU is discarded.

5. The device according to claim 1, wherein: The DRB is an acknowledged mode (AM) DRB.

6. The device according to claim 1, wherein: The at least one processor is further configured to: A configuration is received for a status prohibit timer associated with a lost PDU or a status report prohibit timer associated with a PDU discard, wherein the discard status report is associated with the status prohibit timer or the status report prohibit timer.

7. The device according to claim 6, wherein: The discard status report is sent at a time corresponding to expiration of the status prohibit timer or the status report prohibit timer.

8. The device according to claim 1, wherein: The discard status report indicates at least one sequence number of the at least one PDU using an acknowledgment field.

9. The device according to claim 1, wherein: The discard status report comprises at least one additional field compared to at least one other discard status report, wherein the at least one additional field comprises at least one sequence number of the at least one PDU.

10. The apparatus according to claim 1, further comprising: At least one of a transceiver or an antenna coupled to the at least one processor, wherein the at least one processor is configured to send the discard status report via at least one of the transceiver or the antenna.

11. An apparatus for wireless communication at a second wireless device, comprising: Memory; as well as at least one processor coupled to the memory and based at least in part on the information stored in the memory, the at least one processor is configured to: communicating, with a first wireless device, a plurality of protocol data units (PDUs) associated with a data radio bearer (DRB); receiving, from the first wireless device, a discard status report associated with at least one PDU of the plurality of PDUs that satisfies at least one discard criterion; as well as The sliding window of the DRB is updated based on the discard status report.

12. The device according to claim 11, wherein The at least one processor is further configured to: An indication is sent to a packet data convergence protocol (PDCP) layer indicating that each radio link control (RLC) service data unit (SDU) in a set of RLC SDUs associated with the at least one PDU has been discarded.

13. The device according to claim 11, wherein: The plurality of PDUs are associated with an extended reality (XR) service.

14. The device according to claim 11, wherein: The second wireless device maintains an acknowledgement state variable and a transmission state variable, wherein a sequence number of a radio link control (RLC) service data unit (SDU) associated with the at least one PDU associated with the discard status report is greater than or equal to a first value of the acknowledgement state variable and less than or equal to a second value of the transmission state variable, wherein to update the sliding window of the DRB based on the discard status report, the at least one processor is configured to: The first value of the acknowledgment state variable is set equal to the sequence number, wherein the RLC SDU belongs to a set of RLC SDUs for which the second wireless device has not received a positive acknowledgment, wherein the sequence number is less than each sequence number of the set of RLC SDUs.

15. The apparatus according to claim 11, further comprising: At least one of a transceiver or an antenna coupled to the at least one processor, wherein the at least one processor is configured to receive the discard status report via at least one of the transceiver or the antenna.

16. An apparatus for wireless communication at a first wireless device, comprising: Memory; as well as at least one processor coupled to the memory and based at least in part on the information stored in the memory, the at least one processor is configured to: communicating, with a second wireless device, a plurality of protocol data units (PDUs) associated with a data radio bearer (DRB); receiving, from the second wireless device, an indication of a sequence number gap associated with at least one PDU in the plurality of PDUs based on expiration of a Packet Data Convergence Protocol (PDCP) discard timer; and The sliding window of the DRB is updated based on the sequence number gap.

17. The device according to claim 16, wherein: The DRB is an acknowledged mode (AM) DRB.

18. The device according to claim 16, wherein: The indication of the sequence number gap is included in a control PDU.

19. The device according to claim 18, wherein: The control PDU includes: a first field indicating that the control PDU is used for control, indicating that the control PDU includes a second field of a discard indication, a third field comprising said indication of said sequence number gap, and A fourth field also indicates a discard indication.

20. The device according to claim 16, wherein: The plurality of PDUs are associated with an extended reality (XR) service.

21. The device according to claim 16, wherein: The first wireless device maintains a maximum state transmit variable and a receive state variable, and wherein, to update a sliding window of the DRB based on the sequence number gap, the at least one processor is configured to: If the sequence number gap is equal to a first value of the maximum state send variable, updating the first value of the maximum state send variable to be equal to a sequence number of a radio link control (RLC) service data unit (SDU) for each byte not yet received, wherein the sequence number is greater than the first value; or If the sequence gap number is equal to a second value of the reception state variable, updating the second value of the reception state variable to be equal to the sequence number of the RLC SDU for each byte of which has not been received, wherein the sequence number is greater than the second value.

22. The apparatus of claim 16, further comprising: At least one of a transceiver or an antenna coupled to the at least one processor, wherein the at least one processor is configured to receive the indication of the sequence number gap via at least one of the transceiver or the antenna.

23. An apparatus for wireless communication at a second wireless device, comprising: Memory; as well as at least one processor coupled to the memory and based at least in part on the information stored in the memory, the at least one processor is configured to: communicating, with a first wireless device, a plurality of protocol data units (PDUs) associated with a data radio bearer (DRB); detecting an expiration of a Packet Data Convergence Protocol (PDCP) discard timer associated with at least one PDU of the plurality of PDUs; as well as An indication of a sequence number gap associated with the at least one PDU in the plurality of PDUs is sent to the first wireless device based on the expiration of the PDCP discard timer.

24. The device according to claim 23, wherein: The DRB is an acknowledged mode (AM) DRB.

25. The device according to claim 23, wherein The indication of the sequence number gap is included in a control PDU.

26. The device according to claim 25, wherein The control PDU includes: a first field indicating that the control PDU is used for control, indicating that the control PDU includes a second field of a discard indication, a third field comprising said indication of said sequence number gap, and A fourth field also indicates a discard indication.

27. The device according to claim 23, wherein: The at least one processor is further configured to: obtaining a discard indication indicating that the at least one PDU is to be discarded; and The at least one PDU is discarded based on the discard indication.

28. The device according to claim 27, wherein To discard the at least one PDU based on the discard indication, the at least one processor is configured to: Each radio link control (RLC) service data unit (SDU) in a set of RLC SDUs associated with the at least one PDU is discarded.

29. The device according to claim 27, wherein: When the discard indication is obtained, the PDCP discard timer is started.

30. The apparatus of claim 23, further comprising: At least one of a transceiver or an antenna coupled to the at least one processor, wherein the at least one processor is configured to transmit the indication of the sequence number gap via the at least one of the transceiver or the antenna.

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