Method and apparatus of protocol data convergence protocol sequence number gap report handling for extended reality

Abstract

The disclosure relates to a 5G or 6G communication system for supporting higher data transmission rates and satisfying various service requirements. A method performed by a UE in a wireless communication system is provided. The method may include: transmitting, to a source base station, a first PDCP SN gap report; identifying that the first PDCP SN gap report has been transmitted by a transmitting PDCP entity of the UE during a mobility operation of the UE; and in case that the successful delivery of the first PDCP SN gap report is not confirmed by the lower layers of the UE, transmitting, to a target base station, a second PDCP SN gap report including discard information for at least one PDCP SDU indicated as discarded in the first PDCP SN gap report.

Description

METHOD AND APPARATUS OF PROTOCOL DATA CONVERGENCE PROTOCOL SEQUENCE NUMBER GAP REPORT HANDLING FOR EXTENDED REALITY

[0001] The disclosure pertains to the field of wireless communication and / or mobile communication. More particularly, the disclosure relates to a method and apparatus for handling protocol data convergence protocol (PDCP) sequence number (SN) gap reports in the context of extended reality (XR) applications.

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

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

[0004] In order to accomplish such a high data rate and an ultra-low latency, it has been considered to implement 6G communication systems in a terahertz band (for example, 95GHz to 3THz bands). It is expected that, due to severer path loss and atmospheric absorption in the terahertz bands than those in mmWave bands introduced in 5G, technologies capable of securing the signal transmission distance (that is, coverage) will become more crucial. It is necessary to develop, as major technologies for securing the coverage, radio frequency (RF) elements, antennas, novel waveforms having a better coverage than orthogonal frequency division multiplexing (OFDM), beamforming and massive multiple input multiple output (MIMO), full dimensional MIMO (FD-MIMO), array antennas, and multiantenna transmission technologies such as large-scale antennas. In addition, there has been ongoing discussion on new technologies for improving the coverage of terahertz-band signals, such as metamaterial-based lenses and antennas, orbital angular momentum (OAM), and reconfigurable intelligent surface (RIS).

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

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

[0007] Extended reality (XR) is an umbrella term that encompasses various forms of digital realities, including virtual reality (VR), augmented reality (AR), and mixed reality (MR). XR is considered an essential technology for the realization of digital twin and meta-universe environments. XR has been incorporated as an agreed work item in 5G Advanced, specifically in 3GPP Release 18, which targets the provision of a communication system framework capable of fulfilling the requirements of high data rates, very low latency, and power-efficient connectivity for XR applications.

[0008] In such communication systems, the packet data convergence protocol (PDCP) is a Layer-2 sub-layer responsible for the data plane processing of transmitted and received packets. PDCP functionalities include, but are not limited to, service data unit (SDU) discard, ciphering and integrity protection, header compression on the transmitting side, and reordering, deciphering, integrity verification, duplicate discarding, and header decompression on the receiving side. Each radio bearer (RB) is associated with a transmitting PDCP entity and / or a receiving PDCP entity. The SDU discard procedure may be triggered upon the expiry of an associated discard timer or upon confirmation of the successful delivery of a PDCP SDU from a peer PDCP entity, for example, through a PDCP status report.

[0009] For XR applications, existing PDCP SDU discard mechanisms may not be efficient or effective. XR traffic is more tightly coupled with frame-level transmission rather than Internet Protocol (IP) packet transmission, which is typically mapped one-to-one to a PDCP SDU. Accordingly, an enhanced discard mechanism has been introduced that considers discarding at a PDU Set level, for example, a group of SDUs belonging to the same frame or slice.

[0010] However, certain issues still remain. When a PDCP SDU is discarded, a PDCP SN gap may occur. Upon reception of subsequent SDUs, the receiving PDCP entity may initiate or continue a reordering timer due to the SN gap. Upon expiry of the reordering timer, the receiver entity realizes the loss of the SDUs with the associated SN. The wait for the expiry of the reordering timer may result in delayed delivery of received SDUs, thereby impacting latency-sensitive XR services. In association with discard operations, a PDCP Sequence Number (SN) gap report may be transmitted from a transmitting PDCP entity to a receiving PDCP entity to inform about discarded PDCP SDUs.

[0011] Additional challenges arise during mobility procedures. A User Equipment (UE) may discard certain PDCP SDUs prior to handover and may inform a source network entity, such as a source gNB (or equivalent entity for 6G e.g., may be termed as sNB or aNB or iNB), through a PDCP SN gap report. During handover, the source gNB forwards buffered packets along with Sequence Numbers (SNs) corresponding to PDCP packets not received in an SN Status Transfer message to a target network entity, such as a target gNB. However, the target gNB may attempt retransmission of PDCP packets that were already discarded by the UE, as the target gNB may not have received the corresponding PDCP SN gap report. Consequently, the target gNB may be unaware of the discard status of such PDCP SDUs, leading to unnecessary retransmission attempts and excessive delay due to reordering operations.

[0012] Further ambiguity may arise when a receiving PDCP entity receives two or more PDCP SN gap reports sequentially conveying discard information for the same PDCP SDU. In cases where the reports convey different or inconsistent discard information, the receiving entity may face uncertainty in determining the actual discard status of the PDCP SDU. Such ambiguity may adversely affect reordering and delivery operations, thereby necessitating a standardized mechanism to resolve discrepancies associated with multiple PDCP SN gap reports.

[0013] Thus, it is desired to address the above-mentioned disadvantages, issues, or other shortcomings, or at least provide a useful alternative.

[0014] The disclosure relates to a method and apparatus for handling protocol data convergence protocol (PDCP) sequence number (SN) gap reports in the context of extended reality (XR) applications.

[0015] Accordingly, an aspect of the disclosure is to provide a method and apparatus for handling PDCP SN gap reporting for the XR applications and during mobility procedures.

[0016] An aspect of the disclosure is to provide a method for triggering sending or resending PDCP SN gap reports during mobility or when the upper layer requests a PDCP entity re-establishment.

[0017] An aspect of the disclosure is to provide a method to enhance discard information for incompletely submitted SDU(s) due to the "stop retransmission of discarded SDU" feature.

[0018] An aspect of the disclosure is to provide a method to trigger a PDCP SN gap report when at least one byte for the discarded PDCP SDU(s) is not submitted by any RLC entity to lower layers when the "stop retransmission of discarded SDU" feature is configured.

[0019] An aspect of the disclosure is to provide a method to handle ambiguities that arise when two or more PDCP SN gap reports convey different discard information for the same PDCP SDU.

[0020] The technical problems to be achieved in the various examples of the disclosure are not limited to those mentioned above, and other technical problems not mentioned can be considered by a person having ordinary skill in the art from the various examples of the disclosure described below.

[0021] According to an aspect of the disclosure, a method performed by a user equipment (UE) in a wireless communication system is provided.　The method may include: transmitting, to a source base station, a first packet data convergence protocol (PDCP) sequence number (SN) gap report; identifying that the first PDCP SN gap report has been transmitted by a transmitting PDCP entity of the UE during a mobility operation of the UE; determining whether a successful delivery of the first PDCP SN gap report is confirmed by lower layers of the UE; and in case that the successful delivery of the first PDCP SN gap report is not confirmed by the lower layers of the UE, transmitting, to a target base station, a second PDCP SN gap report including discard information for at least one PDCP service data unit (SDU) indicated as discarded in the first PDCP SN gap report.

[0022] According to an aspect of the disclosure, a user equipment (UE) in a wireless communication system is provided. The UE may include: a transceiver; a processor coupled to the transceiver; and memory coupled to the processor storing instructions executable by the processor, wherein the instructions cause the UE to: transmit, to a source base station, a first packet data convergence protocol (PDCP) sequence number (SN) gap report, identify that the first PDCP SN gap report has been transmitted by a transmitting PDCP entity of the UE during a mobility operation of the UE, determine whether a successful delivery of the first PDCP SN gap report is confirmed by lower layers of the UE, and in case that the successful delivery of the first PDCP SN gap report is not confirmed by the lower layers of the UE, transmit, to a target base station, a second PDCP SN gap report including discard information for at least one PDCP service data unit (SDU) indicated as discarded in the first PDCP SN gap report.

[0023] An aspect of the disclosure provides a method for reporting PDCP SN gaps in the UE. Further, the method includes transmitting by the UE a PDCP SN gap report in an uplink direction towards a network. Further, the method includes determining by the UE that a transmitting PDCP entity has previously transmitted a PDCP SN gap report during mobility. Further, the method includes determining by the UE whether successful delivery of the PDCP SN gap report is confirmed by lower layers. Further, the method includes triggering or sending or retransmitting the PDCP SN gap report for the at least one of same set of previously discarded PDCP Service Data Units (SDUs) and any newly discarded PDCP SDUs in response to determining that successful delivery of the PDCP SN gap report is not confirmed by the lower layers.

[0024] An aspect of the disclosure provides a method for reporting PDCP SN gaps in the UE. The method includes determining by the UE that PDCP SDUs are discarded and that at least one stored PDCP SDU is associated with a COUNT value larger than the COUNT value associated with the discarded PDCP SDU. Further, the method includes determining by the UE whether at least one segment of the discarded PDCP SDU is not submitted by any Radio Link Control (RLC) entity to lower layers when stop retransmission of Obsolete SDU (stopReTxObsoleteSDU) is enabled for the Acknowledged Mode (AM) Data Radio Bearers (DRBs). Further, the method includes triggering by the UE the PDCP SN gap report if at least one segment of the discarded PDCP SDU is not submitted by any RLC entity to lower layers. Further, the method includes determining by the UE whether the discarded PDCP SDU(s) have not been submitted by any RLC entity to lower layers when stop retransmission of Obsolete SDU (stopReTxObsoleteSDU) is not enabled for the AM DRBs. Further, the method includes triggering by the UE the PDCP SN gap report when the discarded PDCP SDU(s) have not been submitted by any RLC entity to lower layers.

[0025] An aspect of the disclosure provides a UE for reporting PDCP SN. Further, the UE includes a memory, a processor, and a PDCP SN Gap report Controller. Further, the PDCP SN Gap report Controller is coupled to the memory and the processor. Further, the PDCP SN Gap report Controller transmits the PDCP SN gap report in the uplink direction towards the network entity . Further, the PDCP SN Gap report Controller determines that a transmitting PDCP entity has previously transmitted the PDCP SN gap report during mobility. Further, the PDCP SN Gap report Controller determines whether successful delivery of the PDCP SN gap report is confirmed by lower layers. Further, the PDCP SN Gap report Controller triggers or sends or retransmits the PDCP SN gap report for the at least one of same set of previously discarded PDCP Service Data Units (SDUs) and any newly discarded PDCP SDUs in response to determining that successful delivery of the PDCP SN gap report is not confirmed by the lower layers.

[0026] An aspect of the disclosure provides a UE for reporting PDCP SN. Further, the UE includes a memory, a processor, and a PDCP SN Gap report controller. The PDCP SN Gap report controller determines PDCP Service Data Units (SDUs) are discarded and at least one stored PDCP SDU is associated with a COUNT value larger than the COUNT value associated with the discarded PDCP SDU. Further, the PDCP SN Gap report controller determines whether at least one segment of the discarded PDCP SDU is not submitted by any Radio Link Control (RLC) entity to lower layers when stop retransmission of Obsolete SDU (stopReTxObsoleteSDU) is set as enabled for the Acknowledged Mode (AM) Data Radio Bearers (DRBs). Further, the PDCP SN Gap report controller triggers a PDCP Sequence Number (SN) gap report when at least one segment of the discarded PDCP SDU is not submitted by any RLC entity to lower layers. Further, the PDCP SN Gap report controller determines whether the discarded PDCP SDU(s) are not submitted by any RLC entity to the lower layers when stop retransmission of Obsolete SDU (stopReTxObsoleteSDU) is not set as enabled for the AM DRBs. Further, the PDCP SN Gap report controller triggers the PDCP SN gap report when the discarded PDCP SDU(s) have not been submitted by any RLC entity to the lower layers.

[0027] These and other aspects of the examples herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred examples and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the examples herein, and the examples herein include all such modifications.

[0028] According to an example of the present disclosure, by triggering or retransmitting a PDCP SN gap report when successful delivery of a previously transmitted PDCP SN gap report is not confirmed by lower layers, unnecessary retransmission of already-discarded PDCP SDUs by a target network entity can be avoided, thereby reducing latency and improving resource efficiency for XR services.

[0029] According to an example of the present disclosure, by triggering a PDCP SN gap report when at least one segment of a discarded PDCP SDU has not been submitted by any RLC entity to lower layers, the receiving PDCP entity can be notified of the discard status of incompletely submitted SDUs in a timely manner, thereby preventing reordering delay caused by missing discard information.

[0030] According to an example of the present disclosure, by determining the actual discard status based on all received PDCP SN gap reports, ambiguities arising from two or more PDCP SN gap reports conveying different discard information for the same PDCP SDU can be resolved, thereby enhancing the reliability of reordering and delivery operations at the receiving PDCP entity.

[0031] The effects that can be obtained from the disclosure are not limited to the effects mentioned in the various examples, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the disclosure belongs from the description below.

[0032] These and other features, aspects, and advantages of the disclosure are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The examples herein will be better understood from the following description with reference to the drawings, in which:

[0033] Figure 1a is a schematic diagram that illustrates a PDCP SN gap occurring during a mobility procedure according to the disclosure.

[0034] Figure 1b is a schematic diagram that illustrates a missing discard status for incompletely submitted SDUs according to the disclosure.

[0035] Figure 1c is a schematic diagram that illustrates receiver confusion in handling PDCP SN gap reports according to the disclosure.

[0036] Figure 2 is a block diagram that illustrates the UE for reporting PDCP SN gaps during mobility according to examples of the disclosure.

[0037] Figure 3 is a flow diagram that illustrates a method for reporting PDCP SN gaps in the UE according to examples of the disclosure.

[0038] Figure 4 is a flow diagram that illustrates a method for triggering PDCP SN gap reports in the UE according to examples of the disclosure.

[0039] Figure 5 illustrates a flow diagram of PDCP SN gap reporting during mobility according to examples of the disclosure.

[0040] Figure 6 illustrates a flow diagram of PDCP SN gap report triggering at the UE according to examples of the disclosure.

[0041] Figure 7 illustrates a flow diagram of PDCP SN gap report handling at the receiving PDCP entity of the UE according to examples of the disclosure.

[0042] The examples herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting examples that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the examples herein. Also, the various examples described herein are not necessarily mutually exclusive, as some examples can be combined with one or more other examples to form new examples. The term "or"as used herein, refers to a non-exclusive or, unless otherwise indicated. The examples used herein are intended merely to facilitate an understanding of ways in which the examples herein can be practiced and to further enable those skilled in the art to practice the examples herein. Accordingly, the examples are not to be construed as limiting the scope of the examples herein.

[0043] As is traditional in the field, examples are described and illustrated in terms of blocks that carry out a described function or functions.　These blocks, which are referred to herein as managers, units, modules, hardware components or the like, are physically implemented by analog and / or digital circuits such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits and the like, and optionally be driven by firmware and software. The circuits, for example, may be embodied in one or more semiconductor chips, or on substrate supports such as printed circuit boards and the like.　The circuits constituting a block be implemented by dedicated hardware, or by a processor (e.g., one or more programmed microprocessors and associated circuitry), or by a combination of dedicated hardware to perform some functions of the block and a processor to perform other functions of the block. Each block of the examples be physically separated into two or more interacting and discrete blocks without departing from the scope of the proposed method.　Likewise, the blocks of the examples be physically combined into more complex blocks without departing from the scope of the proposed method.

[0044] The accompanying drawings facilitate understanding of various technical features. The examples are not limited by these drawings and extend to any alterations, equivalents, and substitutes. Terms like first, second, etc., are used for distinction and do not limit the elements.

[0045] Figure 1a is a schematic diagram illustrating a packet data convergence protocol (PDCP) sequence number (SN) gap occurring during a mobility procedure according to the the disclosure. Initially, a mobile device (103) is served by a network entity such as source gNB (101) (or equivalent entity for 6G) and is configured to undergo handover to a target gNB (102). During a mobility scenario, the mobile device (103) may discard one or more PDCP Service Data Units (SDUs) prior to the execution of a handover from the source gNB (101) to the target gNB (102). The mobile device (103) may transmit a PDCP SN gap report to the source gNB (101), indicating sequence numbers corresponding to the discarded PDCP SDUs. There is a possibility that the PDCP SN gap report transmitted during a mobility scenario may not be successfully received due to degraded channel conditions during handover. Further, during the handover procedure, the source gNB (101) forwards buffered PDCP packets to the target gNB (102). This forwarding may be performed along with corresponding PDCP sequence numbers through an SN STATUS TRANSFER message, indicating PDCP packets that are not received by the mobile device (103).

[0046] However, the target gNB (102) may attempt retransmission of PDCP packets identified as not received without being aware that certain PDCP SDUs corresponding to those sequence numbers were previously discarded by the mobile device (103) prior to handover. The existing system lacks a mechanism to ensure that the PDCP SN gap report transmitted prior to mobility is successfully delivered to the target gNB (102), thereby resulting in unnecessary retransmissions and degraded performance.

[0047] Figure 1b is a schematic diagram illustrating a missing discard status for incompletely submitted SDUs according to the example of the disclosure. A transmitting side (Tx) or source network entity such as source gNB (101) includes a PDCP entity (104a) and an RLC entity (105a), while a receiving side (Rx) or target gNB (102) includes a PDCP entity (104b) and an RLC entity (105b). In conventional operation, the transmitting PDCP entity (104a) may discard the PDCP SDU corresponding to sequence number SN3. With Release 19 AM RLC enhancements, including stopReTxDiscardedSDU, SN3 may be incompletely submitted to the lower layer (107), for example, from the PDCP entity (104a) to the RLC entity (105a) in the form of one or more SDU segments. Upon receipt of a discard indication at the transmitting PDCP entity (104a), the corresponding SDU becomes obsolete while being only partially processed at the RLC layer.

[0048] In such a case, the incompletely submitted SDU is not delivered to the receiving PDCP entity (104b). Instead, at the receiving side (102), the corresponding SDU is discarded at the RLC entity (105b) after t-RxDiscard expiry (109). Further, the PDCP SN gap report for SN3 is not triggered (106) under the legacy triggering conditions. Consequently, the receiving PDCP entity (104b) does not obtain information regarding the discard status of the incompletely submitted SDU corresponding to SN3. Due to the absence of discard status information, reordering operations at the receiving PDCP entity (104b) experience reordering delay for SN3 (108), thereby causing excessive delay in the prior art. The existing system lacks a mechanism to trigger the PDCP SN gap report when at least one segment of the discarded PDCP SDU is not submitted by any RLC entity to lower layers, particularly when the stopReTxObsoleteSDU feature is configured.

[0049] Figure 1c is a schematic diagram illustrating receiver confusion in handling PDCP SN gap reports according to the disclosure. The transmitting PDCP entity (104a) may discard one or more PDCP SDUs and inform the receiving PDCP entity (104b) through a PDCP SN gap report. Upon reception of the PDCP SN gap report, the receiving PDCP entity (104b) updates a Receive_Delivery (RX_DELIV) state variable to a COUNT value of a first PDCP SDU that is not delivered to upper layers and is not discarded, where the COUNT includes a hyper frame number and a sequence number. Ambiguity arises when two or more PDCP SN gap reports convey different discard information for the same PDCP SDU. As illustrated in Figure 1C, the receiving PDCP entity (104b) may receive two PDCP SN gap reports (110).

[0050] In a first scenario, the PDCP SDU corresponding to sequence number SN3 may be indicated as discarded in a first PDCP SN gap report (Gap report A) by setting a corresponding bit to '1' and subsequently indicated as not discarded in a second PDCP SN gap report (Gap report B) by setting the corresponding bit to '0'. If the receiving PDCP entity (104b) receives Gap report A earlier than Gap report B, contradictory discard status information is observed for the same PDCP SDU, thereby creating uncertainty in updating RX_DELIV. In a second scenario involving out-of-sequence reception, Gap report A may indicate SN3 as not discarded (bit set to '0') and Gap report B may indicate SN3 as discarded (bit set to '1'). If the receiving PDCP entity (104b) receives Gap report B earlier than Gap report A, inconsistent discard status information is again observed.

[0051] In both scenarios, the receiving PDCP entity (104b) encounters ambiguity in determining the correct discard status of the PDCP SDU, resulting in uncertainty in RX_DELIV state variable handling and potential reordering delay. The existing system lacks a mechanism to handle ambiguities when two or more PDCP SN gap reports convey different discard information for the same PDCP SDU.

[0052] To overcome these drawbacks in the existing system, there is a need for enhanced PDCP SN gap reporting mechanisms for XR services. Specifically, there is a need for a mechanism to ensure reliable delivery of the PDCP SN gap report to the target network entity such as gNB (102) during mobility, to handle incompletely submitted PDCP SDUs when the stopReTxObsoleteSDU feature is configured, and to resolve ambiguities at the receiving PDCP entity when two or more PDCP SN gap reports convey different discard information for the same PDCP SDU.

[0053] Figure 2 is a block diagram that illustrates the UE (201) for reporting PDCP SN gaps according to examples as disclosed herein. Examples of the UE (201) can include, but are not limited to, Consumer Electronics (such as Mobile Phones and Smartphones), Tablets, Wearable Devices, Television, Computing Devices (such as Laptops, Notebooks, Desktops, Workstations, etc.), IoT Devices, Automotive Systems (such as connected cars, Autonomous Vehicles, Vehicle-to-Everything (V2X) communication devices, etc.), Enterprise Devices such as robotics, Specialized Equipment (such as Medical Devices, Public Safety Devices, etc.), Media Devices (such as Gaming Consoles, Streaming Devices, etc.). Examples of the wireless communication network system include, but are not limited to, Cellular Networks (such as 2G, 3G, 4G, 5G, Beyond 5G (B5G) / 6G or advanced cellular networks), Local Area Networks (LANs) (such as Wi-Fi, Li-Fi, etc.), Personal Area Networks (PANs) (such as Bluetooth, Zigbee, Z-Wave, etc.), Wide Area Networks (WANs) (such as Satellite Communication Networks, Long Range Wide Area Network, Narrowband IoT, Low-bandwidth communication for IoT, etc.), Metropolitan Area Networks (MANs), Machine-to-Machine (M2M), Ad Hoc and Mesh Networks, Emerging and Advanced Networks.

[0054] The UE (201) includes the processor (202), the memory (204), an I / O interface (203), a PDCP layer (205), and a PDCP SN Gap report Controller (206). The processor (202) of the UE (201) communicates with the memory (204), the I / O interface (203), and PDCP SN Gap report Controller (206). The processor (202) is configured to execute instructions stored in the memory (204) and to perform various processes. The processor (202) can include one or a plurality of processors, can be a general-purpose processor such as a central processing unit (CPU), an application processor (AP), or the like, a graphics-only processing unit such as a graphics processing unit (GPU), a visual processing unit (VPU), and / or an Artificial Intelligence (AI) dedicated processor such as a neural processing unit (NPU).

[0055] The memory (204) of the UE (201) includes storage locations addressable through the processor (202). The memory (204) can be a volatile memory, a non-volatile memory, or a combination of both. The memory (204) can include one or more computer-readable storage media such as magnetic hard discs, optical discs, floppy discs, flash memories, electrically programmable memories (EPROM), or electrically erasable and programmable memories (EEPROM).

[0056] The I / O interface (203) facilitates transmission of information between the memory (204) and external peripheral devices associated with the UE (201). The I / O interface (203) receives information from the UE (201) and communicates the same to the external peripheral devices.

[0057] The PDCP layer (205) of the UE (201) is configured to manage the transmitting PDCP entity and the receiving (Rx) PDCP entity for handling PDCP SN gap reporting. The PDCP layer (205) communicates with the PDCP SN Gap report Controller (206) to facilitate triggering, sending, or retransmitting of the PDCP SN gap report during mobility.

[0058] The PDCP SN Gap report Controller (206) is coupled to the memory (204) and the processor (202). This coupling allows for efficient data transfer and communication between the components, ensuring that the PDCP SN Gap report Controller (206) can access and process PDCP SN gap report data in real-time. The PDCP SN Gap report Controller (206) is an innovative integrated circuit that is implemented in the UE (201). In an example, the structure of such innovative integrated circuit includes a multi-core architecture that enables dynamic management of PDCP SN gap reporting during mobility in wireless networks. Each core is optimized for specific tasks such as monitoring successful delivery confirmation from lower layers, managing discarded PDCP SDUs, triggering or retransmitting PDCP SN gap reports during mobility events, and updating RX_DELIV parameters at the receiving PDCP entity. The innovative integrated circuit for the management of PDCP SN gap reporting in the UE (201) is made of a combination of analog and digital components designed to optimize power consumption and performance of the PDCP SN gap reporting mechanism. The analog components include a low-noise amplifier and a high-precision analog-to-digital converter to ensure accurate signal processing. The digital components include a microcontroller unit (MCU) and a digital signal processor (DSP) that work in tandem to dynamically manage the PDCP SN gap reporting based on mobility conditions and lower layer delivery confirmations.

[0059] Further, the PDCP SN Gap report Controller (206) transmits a PDCP SN gap report in the uplink direction towards the network entity. The network entity may include gNodeB (gNB) or 6G equivalent network entity. Further, the PDCP SN Gap report Controller (206) determines that a transmitting PDCP entity has previously transmitted a PDCP SN gap report during mobility. Further, the PDCP SN Gap report Controller (206) determines whether successful delivery of the PDCP SN gap report is confirmed by lower layers. Further, the PDCP SN Gap report Controller (206) triggers, sends, or retransmits the PDCP SN gap report for the same set of previously discarded PDCP SDUs and any newly discarded PDCP SDUs in response to determining that successful delivery of the PDCP SN gap report is not confirmed by the lower layers. Further, the UE determines that the transmitting PDCP entity has previously transmitted the PDCP SN gap report at least one of prior to re-establishment and one second prior to reception of a Radio Resource Control (RRC) reconfiguration. Further, the PDCP SN Gap report Controller (206) of the UE (201) may determine that the transmitting PDCP entity has previously transmitted the PDCP SN gap report at least once prior to re-establishment and once prior to reception of a Radio Resource Control (RRC) reconfiguration message. Further, the PDCP SN Gap report Controller (206) may determine that the PDCP SN gap report was previously transmitted and that it was transmitted within a predetermined time interval before reception of the RRC reconfiguration message. Further, the predetermined time interval is 1 second. Further, the PDCP SN Gap report Controller (206) may trigger, send, or retransmit the PDCP SN gap report. Further, the PDCP SN Gap report Controller (206) may submit or resubmit the stored PDCP SN gap report to lower protocol layers.

[0060] Further, the PDCP SN Gap report Controller (206) may set a First Discarded COUNT (FDC) field to the smallest COUNT value among the COUNT values associated with the discarded PDCP SDUs. Further, the PDCP SN Gap report Controller (206) may trigger, send, or retransmit the PDCP SN gap report. Further, the PDCP SN Gap report Controller (206) may allocate a discard bitmap field when more than one PDCP SDU is discarded. Further, the PDCP SN Gap report Controller (206) may set bits in the discard bitmap field to '1' for discarded PDCP SDUs and to '0' for all other PDCP SDUs. Further, the PDCP SN Gap report Controller (206) may submit the PDCP SN gap report to lower layers.

[0061] Further, the PDCP SN Gap report Controller (206) may determine that the transmitting PDCP entity has previously transmitted the PDCP SN gap report. Further, the PDCP SN Gap report Controller (206) may determine that the PDCP SN gap report was previously transmitted after receiving a Radio Resource Control (RRC) reconfiguration message. The RRC reconfiguration message is applied due to a conditional reconfiguration execution. Further, the PDCP SN Gap report Controller (206) performs retransmission of the PDCP SN gap report previously submitted to re-established or released AM RLC entities for which successful delivery is not confirmed by lower layers when upper layers request a PDCP data recovery for the AM DRB.

[0062] The PDCP SN Gap report Controller allows for efficient data transfer and communication between the components, ensuring that the PDCP SN Gap report Controller (206) may access and process PDCP SN gap report data in real-time. The PDCP SN Gap report Controller (206) includes a multi-core architecture that enables dynamic management of PDCP SN gap reporting in wireless networks. Each core is optimized for specific tasks such as determining that PDCP SDUs are discarded and at least one stored PDCP SDU is associated with a COUNT value larger than the COUNT value associated with the discarded PDCP SDU, determining whether at least one segment for the discarded PDCP SDU is not submitted by any RLC entity to lower layers based on the stopReTxObsoleteSDU configuration, triggering the PDCP SN gap report accordingly, receiving two or more PDCP SN gap reports at the Rx PDCP entity conveying discard information for the same PDCP SDU, determining the status for the PDCP SDU as actually discarded or actually non-discarded, and updating the RX_DELIV parameter to assign an actual non-discarded status to the PDCP SDU. The innovative integrated circuit for the management of PDCP SN gap reporting in the UE (201) is made of a combination of analog and digital components designed to optimize power consumption and performance of the PDCP SN gap reporting mechanism. The analog components include a low-noise amplifier and a high-precision analog-to-digital converter to ensure accurate signal processing. The digital components include a microcontroller unit (MCU) and a digital signal processor (DSP) that work in tandem to dynamically manage the PDCP SN gap reporting based on discard conditions and stopReTxObsoleteSDU configuration.

[0063] Further, the PDCP SN Gap report Controller (206) determines that PDCP SDUs are discarded and that at least one stored PDCP SDU is associated with a COUNT value larger than the COUNT value associated with the discarded PDCP SDU. Further, the PDCP SN Gap report Controller (206) determines whether at least one segment of the discarded PDCP SDU is not submitted by any Radio Link Control (RLC) entity to lower layers when stop retransmission of Obsolete SDU (stopReTxObsoleteSDU) is set as enabled for the AM Data Radio Bearer (DRB). Further, the PDCP SN Gap report Controller (206) triggers the PDCP Sequence Number (SN) gap report if at least one segment of the discarded PDCP SDU is not submitted by any RLC entity to lower layers. Further, the PDCP SN Gap report Controller (206) determines whether the discarded PDCP SDU(s) are not submitted by any RLC entity to the lower layers when stopReTxObsoleteSDU is not set as enabled for the AM DRB. Further, the PDCP SN Gap report Controller (206) triggers the PDCP SN gap report when the discarded PDCP SDU(s) are not submitted by any RLC entity to the lower layers. Further, the PDCP SN Gap report Controller (206) receives at a receiving (Rx) PDCP entity two or more PDCP SN gap reports sequentially conveying discard information for the same PDCP SDU. Further, the PDCP SN Gap report Controller (206) determines by the Rx PDCP entity of the UE (201) whether the status for the PDCP SDU is received as discarded in at least one of the received PDCP SN gap reports. Further, the PDCP SN Gap report Controller (206) performs by the Rx PDCP entity of the UE (201) determination of the status for the PDCP SDU as actually discarded when the status for the PDCP SDU is received as discarded in at least one of the received PDCP SN gap reports. Further, the PDCP SN Gap report Controller (206) determines the status for the PDCP SDU as actually non-discarded if the status for the PDCP SDU is not received as discarded in any of the received PDCP SN gap reports. Further, the PDCP SN Gap report Controller (206) updates an RX_DELIV parameter to the COUNT of the first PDCP SDU that is not delivered to upper layers and is not considered as discarded in the PDCP SN gap reports, thereby assigning an actual non-discarded status to the PDCP SDU.

[0064] Further, the PDCP SN Gap report Controller (206) receives a configuration parameter sn-GapReportMobility from upper layers in a radio resource control (RRC) reconfiguration message. The sn-GapReportMobility indicates that the AM DRB is configured to send a PDCP SN gap report during mobility.

[0065] Further, the PDCP SN Gap report Controller (206) performs retransmission of the PDCP SN gap report previously submitted to re-established or released AM RLC entities for which successful delivery is not confirmed by lower layers when upper layers request a PDCP data recovery for the AM DRB.

[0066] Figure 3 is a flow diagram that illustrates a method for reporting PDCP SN gaps in the UE (201) according to examples of the disclosure. At step 301, the method includes transmitting the PDCP SN gap report in an uplink direction towards a network entity such as gNodeB (gNB) by the UE (201). At step 302, the method includes determining that a transmitting PDCP entity has previously transmitted the PDCP SN gap report during mobility by the UE (201). At step 303, the method includes determining whether successful delivery of the PDCP SN gap report is confirmed by lower layers by the UE (201). At step 304, the method includes triggering or sending or retransmitting the PDCP SN gap report for at least one of a same set of previously discarded PDCP service data units (SDUs) and any newly discarded PDCP SDUs in response to determining that successful delivery of the PDCP SN gap report is not confirmed by the lower layers by the UE (201).

[0067] Figure 4 is a flow diagram that illustrates a method for triggering PDCP SN gap reports in the UE (201) according to examples as disclosed herein. At step 401, the method includes determining that PDCP SDUs are discarded and at least one stored PDCP SDU is associated with a COUNT value larger than the COUNT value associated with the discarded PDCP SDU by the UE (201). At step 402, the method includes determining whether at least one segment for the discarded PDCP SDU is not submitted by any Radio Link Control (RLC) entity to lower layers when stop retransmission of Obsolete SDU (stopReTxObsoleteSDU) is set as enabled for the AM Data Radio Bearer (DRB) by the UE (201). At step 403, the method includes triggering the PDCP SN gap report if at least one segment for the discarded PDCP SDU is not submitted by any RLC entity to lower layers by the UE (201). At step 404, the method includes determining whether the discarded PDCP SDU(s) are not submitted by any RLC entity to the lower layers when stop retransmission of Obsolete SDU (stopReTxObsoleteSDU) is not set as enabled for the AM DRB by the UE (201). At step 405, the method includes triggering the PDCP SN gap report when the discarded PDCP SDU(s) are not submitted by any RLC entity to the lower layers by the UE (201).

[0068] Figure 5 illustrates a flow diagram of PDCP SN gap reporting during mobility according to examples as disclosed herein. At step 501, the UE (201) is configured with AM DRBs to send the PDCP SN gap report in an uplink direction towards the network entity such as gNB. At step 502, the UE (201) determines that the transmitting PDCP entity has previously transmitted a PDCP SN gap report during mobility. In option 1, the UE (201) determines that the previous transmission occurred prior to re-establishment. In option 2, the UE (201) determines that the previous transmission occurred one second prior to the reception of an RRC reconfiguration. At step 503, the UE (201) determines whether successful delivery of the PDCP SN gap report is confirmed by lower layers. At step 504, in the case where successful delivery of the PDCP SN gap report is not confirmed by lower layers, the transmitting PDCP entity performs one of the following: In option 1, the transmitting PDCP entity triggers a PDCP SN gap report for the same set of previously discarded PDCP SDUs apart from newly discarded PDCP SDUs, if any. In option 2, the transmitting PDCP entity sends a PDCP SN gap report for the same set of previously discarded PDCP SDUs and optionally or additionally newly discarded PDCP SDUs, if any. In option 3, the transmitting PDCP entity resends or retransmits the PDCP SN gap report for the same set of previously discarded PDCP SDUs.

[0069] Figure 6 illustrates a flow diagram of PDCP SN gap report triggering at the UE (201) according to examples as disclosed herein. At step 601, the UE (201) determines whether AM DRBs are configured by upper layers to send the PDCP SN gap report in the uplink. If the determination is YES, the UE (201) proceeds to step 602. At step 602, the UE (201) determines that PDCP SDU(s) are discarded and there is at least one stored PDCP SDU(s) associated with a COUNT value larger than the COUNT value associated with the discarded PDCP SDU(s). At step 603, the UE (201) determines whether stopReTxObsoleteSDU is set to enabled for the AM DRB. If the determination is YES, the UE (201) proceeds to step 604. If the determination is NO, the UE (201) proceeds to step 605. At step 604, the UE (201) determines whether at least one segment for the discarded PDCP SDU(s) has not been submitted by any RLC entity to lower layers. If the determination is YES, the UE (201) proceeds to step 606. At step 605, the UE (201) determines whether the discarded PDCP SDU(s) has not been submitted by any RLC entity to lower layers. If the determination is YES, the UE (201) proceeds to step 606. At step 606, the transmitting PDCP entity triggers the PDCP SN gap report.

[0070] In an example, the UE (201) conveys the capability and / or support for PDCP SN gap reporting during mobility in a UE capability information message to the network. In an example, the network configures the UE (201) per AM DRB with a configuration parameter termed as sn-GapReportMobility that enables or allows the UE (201) to trigger and / or send the PDCP SN gap report during mobility.

[0071] In an example, the configuration parameter sn-GapReportMobility is signaled to the UE (201) in an RRC reconfiguration message such as a radio bearer configuration, a handover command, a reconfiguration for mobility, or a reconfiguration with sync.

[0072] In an example, the condition or criteria for triggering or sending a PDCP SN gap report during mobility for the AM DRB configured with sn-GapReportMobility is determined as a PDCP SN gap report was previously transmitted during mobility where successful delivery of the PDCP SN gap report is not confirmed by lower layers.

[0073] In an example, the condition or criteria for triggering or sending a PDCP SN gap report during mobility for the AM DRB configured with sn-GapReportMobility is determined as the PDCP SN gap report was previously transmitted prior to PDCP entity re-establishment where successful delivery of the PDCP SN gap report is not confirmed by lower layers.

[0074] In an example, the determination of condition or criteria for triggering or sending the PDCP SN gap report during mobility for the AM DRB configured with sn-GapReportMobility is that the PDCP SN gap report was previously transmitted one second preceding the reception of an RRC reconfiguration or RRC reconfiguration with sync message.

[0075] In an example, determination of condition or criteria for triggering or sending a PDCP SN gap report during mobility for an AM DRB configured with sn-GapReportMobility is that a PDCP SN gap report was previously transmitted during mobility but its successful delivery has not been confirmed by lower layers.

[0076] In an example, determination of condition or criteria for triggering or sending a PDCP SN gap report during mobility for an AM DRB configured with sn-GapReportMobility is that a PDCP SN gap report was previously transmitted prior to PDCP entity reestablishment but its successful delivery has not been confirmed by lower layers.

[0077] In an example, determination of condition or criteria for triggering or sending a PDCP SN gap report during mobility for an AM DRB configured withsn-GapReportMobilityis that a PDCP SN gap report was previously transmitted 1 second preceding the reception of RRC reconfiguration or RRC reconfiguration with sync message.

[0078] In an example, the determination of condition or criteria for triggering or sending the PDCP SN gap report during mobility for the AM DRB configured with sn-GapReportMobility is that the PDCP SN gap report was previously transmitted one second preceding the detection of a radio link failure.

[0079] In an example, the determination of condition or criteria for triggering or sending the PDCP SN gap report during mobility for the AM DRB configured with sn-GapReportMobility is that the PDCP SN gap report was previously transmitted after receiving an RRC reconfiguration message where the RRC reconfiguration message is applied due to a conditional reconfiguration execution.

[0080] In an example, the objects are achieved by providing a system and method for PDCP SN gap reporting during mobility in wireless networks. The method includes determining by the transmitting PDCP entity that for the AM DRB configured by upper layers to send the PDCP SN gap report in the uplink, the PDCP SN gap report was previously transmitted during mobility but its successful delivery is not confirmed by lower layers and triggering by the transmitting PDCP entity the PDCP SN gap report that includes the same set of previously discarded PDCP SDUs apart from newly discarded PDCP SDUs, if any.

[0081] In an example, at least one configuration parameter sn-GapReportMobility is configured for the AM DRB in an RRC signaling message such as in the PDCP config IE in the RRC reconfiguration message to the UE (201) by a network entity such as a gNB.

[0082] In an example, the configuration parameter sn-GapReportMobility indicates whether the AM DRB is configured to perform at least one of triggering and sending the PDCP SN gap report in the uplink when the PDCP SN gap report was previously transmitted during mobility but its successful delivery has not been confirmed by lower layers.

[0083] In an example, the existing configuration parameter sn-GapReport is reused for the purpose of sn-GapReportMobility for the AM DRB to trigger or send the PDCP SN gap report during mobility.

[0084] Example specification for the transmit operation of the discard signaling is provided in the following Example 1, as shown in Table 1.

[0085]

[0086] -In an example, the transmitting PDCP entity stores the PDCP SN gap report (e.g., during a mobility scenario). Further, for AM DRBs configured by upper layers to send the PDCP SN gap report in the uplink (e.g., sn-GapReportMobility), when a PDCP SN gap report was previously transmitted during mobility (e.g., prior to PDCP entity re-establishment) but its successful delivery has not been confirmed by the lower layers, the transmitting PDCP entity shall submit or resubmit a stored PDCP SN gap report to lower layers (i.e., PDCP SN gap report with the same set of discarded PDCP SDUs).

[0087] Example specification for the transmit operation of the PDCP SN gap report is provided in the following Example 2, as shown in Table 2.

[0088]

[0089] Example specification for the transmit operation of the PDCP SN gap report is provided in the following Example 3, as shown in Table 3.

[0090]

[0091] In an example, an example specification for the transmit operation of the PDCP SN gap report is provided in following Example 4, as shown in Table 4.

[0092]

[0093] Example specification for the retransmission operation of the PDCP SN gap report is provided for PDCP data recovery scenario in following Example 5, as shown in Table 5.

[0094]

[0095] In an example, an example specification for sending of the PDCP SN gap report in at least one of the scenarios of PDCP entity re-establishment, PDCP data recovery, uplink data switching, dual active protocol stack (DAPS) release and daps-SourceRelease is provided in following Example 6, as shown in Table 6.

[0096]

[0097] Example specification for sending PDCP SN gap report upon PDCP entity re-establishment is provided in following Example 7, as shown in Table 7.

[0098]

[0099] In an example, an example specification for sending PDCP SN gap report upon PDCP entity re-establishment is provided in following Example 8, as shown in Table 8.

[0100]

[0101] In an example, it is up to UE implementation whether to send or resend a PDCP SN gap report when upper layer requests a PDCP entity re-establishment.

[0102] In an example, the UE indicates its capability to support or not support sending or resending of a PDCP SN gap report when upper layer requests a PDCP entity re-establishment.

[0103] In an example, the disclosure provides a system and method for PDCP SN gap reporting when AM RLC enhancements are applied. The method includes determining by the transmitting PDCP entity whether the conditions are met for triggering a PDCP SN gap report when AM RLC enhancements are applied (e.g., a feature for stopping transmission / retransmission of obsolete SDU, may also be termed asstopReTxObsoleteSDU, is set to enabled for the AM DRB). Further, the method includes triggering of the PDCP SN gap report by the transmitting PDCP entity upon determining whether the conditions are met for triggering a PDCP SN gap report. The conditions include: the PDCP SDU(s) are discarded, and there is at least one stored PDCP SDU which is associated with a COUNT value larger than the COUNT value associated to the discarded PDCP SDU(s) and ifstopReTxObsoleteSDUis set to enabled for the AM DRB and the at least one segment for the discarded PDCP SDU(s) have not been submitted by RLC to lower layers. The advantage is that the receiving PDCP entity is notified with earlier and more information about the discarded SDUs and is enabled to avoid reordering delay.

[0104] Few examples of specification for triggering of the PDCP SN gap report is provided when the AM RLC enhancements are applied in following Examples 9, 10, 11, 12 as shown in Tables 9, 10, 11, 12.

[0105]

[0106]

[0107]

[0108]

[0109] Figure 7 illustrates a flow diagram of PDCP SN gap report handling at the receiving PDCP entity of the UE (201) according to examples of the disclosure.

[0110] At step 701, the receiving PDCP entity of the UE (201) determines that it receives two or more PDCP SN gap reports sequentially conveying discard information for the same PDCP SDU.

[0111] At step 702, the receiving PDCP entity of the UE (201) determines whether the status for the PDCP SDU has been received as discarded in at least one of the received PDCP SN gap reports so far. If the determination is YES, the receiving PDCP entity of the UE (201) proceeds to step 703. If the determination at step 702 is NO, the receiving PDCP entity of the UE (201) proceeds to step 704.

[0112] At step 703, the receiving PDCP entity of the UE (201) determines the status for the PDCP SDU as actually discarded.

[0113] At step 704, the receiving PDCP entity of the UE (201) determines the status for the PDCP SDU as actually non-discarded.

[0114] At step 705, the receiving PDCP entity of the UE (201) updates RX_DELIV to the COUNT value of the first PDCP SDU which has not been delivered to upper layers and has not been considered as discarded in the PDCP SN gap reports; that is, the actual non-discarded status of the PDCP SDU is considered.

[0115] In an example, the Discard Bitmap field indicates which SDUs are reported as discarded and which SDUs are reported as not discarded in the transmitting PDCP entity based on the discarded SDUs triggering the current PDCP SN gap report.

[0116] In an example, the Discard Bitmap field indicates which SDUs are triggering (or have triggered) the PDCP SN gap report and which SDUs are not triggering (or have not triggered) the PDCP SN gap report in the transmitting PDCP entity.

[0117] In an example, an example specification for setting and interpreting the Discard Bitmap for the discard signaling is provided in following Example 13, as shown in Table 13.

[0118]

[0119] In an example, the receiving PDCP entity determines and considers the actual discard status for the SDU when receiving two PDCP SN gap reports including two different discard information for the same PDCP SDU. The receiving PDCP entity updates the Receive_Delivery (RX_DELIV) state variable to the COUNT value (here COUNT includes a hyper frame number and a sequence number) of the first PDCP SDU which has not been delivered to upper layers and is not discarded. However, the receiving PDCP entity may need to react to a situation where different discard statuses for the same PDCP SDU could be received in two (or multiple) different PDCP SN gap reports. For example, PDCP SDU X is reported as bit set to 1 in the PDCP SN gap report A and later PDCP SDU X is reported as bit set to 0 in the PDCP SN gap report B. It is required that the receiving PDCP entity considers the actual non-discarded status and not just the reported non-discarded status (bit set to 0) in the latest PDCP SN gap report. That is, the receiving PDCP entity determines the PDCP SDU X as discarded in this example. Effectively, the receiving PDCP entity regards the discard information in the PDCP SN gap report as reported discarded status (or reported non-discarded status) from this report perspective only and determines the actual discard status (or actual non-discarded status) on the basis of considering all received PDCP SN gap reports so far.

[0120] In an example, the receiving PDCP entity determines the actual non-discarded status for the PDCP SDU when the status for the SDU has been received as non-discarded in all the received PDCP SN gap reports so far.

[0121] In an example, the receiving PDCP entity determines the actual discarded status for the PDCP SDU when the status for the SDU has been received as discarded in at least one of the received PDCP SN gap reports so far.

[0122] In an example, the receiving PDCP entity updates the Receive_Delivery (RX_DELIV) state variable to the COUNT value (here COUNT includes a hyper frame number and a sequence number) of the first PDCP SDU which has not been delivered to upper layers and has not been considered as discarded. That is, the actual non-discarded status of the PDCP SDU is considered.

[0123] In an example, upon reception of the PDCP SN gap report from lower layers, the receiving PDCP entity delivers to upper layers in ascending order of the associated COUNT value after performing header decompression if not decompressed before all stored PDCP SDU(s) with consecutively associated COUNT values starting from COUNT = RX_DELIV + 1, where consecutively associated COUNT value(s) include COUNT value(s) of both the stored PDCP SDU(s) and PDCP SDU(s) which have been considered as discarded (e.g., in at least one of the PDCP SN gap reports so far). The receiving PDCP entity updates RX_DELIV to the COUNT value of the first PDCP SDU which has not been delivered to upper layers and has not been considered as discarded (e.g., in all the PDCP SN gap reports so far) with COUNT value > RX_DELIV.

[0124] In an example, whent-Reorderingexpires, the receiving PDCP entity:

[0125] - delivers to upper layers in ascending order of the associated COUNT value after performing header decompression, if not decompressed before:

[0126] ■ all stored PDCP SDU(s) with associated COUNT value(s) < RX_REORD;

[0127] ■ all stored PDCP SDU(s) with consecutively associated COUNT value(s) starting from RX_REORD, where consecutively associated COUNT value(s) include COUNT value(s) of both the stored PDCP SDU(s) and PDCP SDU(s) which have been considered as discarded (e.g., in at least one of the PDCP SN gap reports so far);

[0128] - update RX_DELIV to the COUNT value of the first PDCP SDU which has not been delivered to upper layers and has not been considered as discarded (e.g., in all PDCP SN gap reports so far), with COUNT value >= RX_REORD;

[0129] In an example, when a PDCP Data PDU is received from lower layers:

[0130] - if RCVD_COUNT = RX_DELIV:

[0131] ■ deliver to upper layers in ascending order of the associated COUNT value after performing header decompression, if not decompressed before;

[0132] □　all stored PDCP SDU(s) with consecutively associated COUNT value(s) starting from COUNT = RX_DELIV, where consecutively associated COUNT value(s) include COUNT value(s) of both the stored PDCP SDU(s) and PDCP SDU(s) which have been considered as discarded (e.g., in at least one of the PDCP SN gap reports so far);

[0133] ■ update RX_DELIV to the COUNT value of the first PDCP SDU which has not been delivered to upper layers and has not been considered as discarded (e.g., in all PDCP SN gap reports so far), with COUNT value > RX_DELIV.

[0134] In an example, an example specification for the operation of the receiving PDCP entity for handling the discard signaling is provided in following Example 14, as shown in Table 14.

[0135]

[0136] In an example, an example specification for the operation of the receiving PDCP entity for handling the discard signaling is provided in following Example 15, as shown in Table 15.

[0137]

[0138] In an example, an example specification for the operation of the receiving PDCP entity for handling the discard signaling is provided in following Example 16, as shown in Table 16.

[0139]

[0140] In an example, the disclosure provides optimized performance for wireless communication systems. Reordering delays are prevented by ensuring accurate and timely reporting of PDCP SN gaps during mobility. Additionally, the disclosure improves mobility performance for Extended Reality (XR) services and enhances the user experience by ensuring seamless continuity of PDCP SN gap reporting during mobility events.

[0141] In another example, the disclosure addresses standardization requirements in wireless communication systems. The existing 3GPP standards gap for XR applications is addressed, providing potential for 6G standardization. Furthermore, the disclosure supports and refers to 5G NR specifications for implementing the UE solutions disclosed herein, however, it is not limited in any sense and can be applied and extended to any other wireless communication systems and associated UE and network entity (e.g., 6G).

[0142] In yet another example, the disclosure ensures accurate behavior in wireless communication systems. Ambiguities in receiver operation are prevented by providing clear and consistent handling of PDCP SN gap reports at the receiving PDCP entity. Proper operation of the stopReTxObsoleteSDU feature is ensured in conjunction with PDCP SN gap reporting, thereby enabling accurate and reliable reporting of discarded PDCP SDUs.

[0143] In an example, the various aspects of PDCP SN gap reporting are addressed, providing a reliable and comprehensive solution. The disclosure ensures that proper discard information reaches the target network entity such as gNB by sending, resending, or triggering the PDCP SN gap report during mobility.

[0144] Further, the disclosure enhances discard information for incompletely submitted PDCP SDU(s) due to the stop retransmission of discarded SDU feature. A PDCP SN gap report is triggered when at least one byte for the discarded PDCP SDU(s) has not been submitted by any RLC entity to lower layers when the stop retransmission of discarded SDU feature is configured. Ambiguities that arise when two or more PDCP SN gap reports convey different discard information for the same PDCP SDU are handled, ensuring accurate and consistent behavior at the receiving PDCP entity.

[0145] The foregoing description of the specific examples will so fully reveal the general nature of the examples herein that others can, by applying current knowledge, readily modify and / or adapt for various applications such specific examples without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed examples. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the examples herein have been described in terms of preferred examples, those skilled in the art will recognize that the examples herein can be practiced with modification within the scope of the examples as described herein.

Claims

1.A method performed by a user equipment (UE) in a wireless communication system,　the method comprising:transmitting, to a source base station, a first packet data convergence protocol (PDCP) sequence number (SN) gap report;identifying that the first PDCP SN gap report has been transmitted by a transmitting PDCP entity of the UE during a mobility operation of the UE;determining whether a successful delivery of the first PDCP SN gap report is confirmed by lower layers of the UE; andin case that the successful delivery of the first PDCP SN gap report is not confirmed by the lower layers of the UE, transmitting, to a target base station, a second PDCP SN gap report including discard information for at least one PDCP service data unit (SDU) indicated as discarded in the first PDCP SN gap report.2.The method of claim 1,wherein the second PDCP SN gap report further includes discard information for at least one newly discarded PDCP SDU.3.The method of claim 1,wherein the first PDCP SN gap report is identified as having been transmitted prior to re-establishment of the transmitting PDCP entity.4.The method of claim 1,wherein the first PDCP SN gap report is identified as having been transmitted within a predetermined time interval before reception of a radio resource control (RRC) reconfiguration message, andwherein the predetermined time interval is 1 second.5.The method of claim 1,wherein the first PDCP SN gap report is identified as having been transmitted after reception of a radio resource control (RRC) reconfiguration message, andwherein the RRC reconfiguration message is applied due to a conditional reconfiguration execution.6.The method of claim 1,wherein the transmission of the second PDCP SN gap report includes submitting or resubmitting the first PDCP SN gap report, stored in the UE, to the lower layers.7.The method of claim 1,wherein the transmission of the second PDCP SN gap report includes:setting, by the transmitting PDCP entity, a first discarded COUNT (FDC) field of the second PDCP SN gap report to a smallest COUNT value among COUNT values associated with the at least one PDCP SDU indicated as discarded;allocating, by the transmitting PDCP entity, a discard bitmap field to the second PDCP SN gap report;setting, by the transmitting PDCP entity, bits in the discard bitmap field to '1' for the at least one PDCP SDU indicated as discarded and to '0' for all other PDCP SDUs within a range of the discard bitmap field; andsubmitting, from the transmitting PDCP entity to the lower layers, the second PDCP SN gap report.8.The method of claim 1, further comprising:receiving, from the source base station, a configuration parameter included in a radio resource control (RRC) reconfiguration message,wherein the configuration parameter indicates that a data radio bearer (DRB) is configured to transmit a PDCP SN gap report to a base station during the mobility operation of the UE.9.A user equipment (UE) in a wireless communication system,　the UE comprising:a transceiver;a processor coupled to the transceiver; andmemory coupled to the processor storing instructions executable by the processor,wherein the instructions cause the UE to:transmit, to a source base station, a first packet data convergence protocol (PDCP) sequence number (SN) gap report,identify that the first PDCP SN gap report has been transmitted by a transmitting PDCP entity of the UE during a mobility operation of the UE,determine whether a successful delivery of the first PDCP SN gap report is confirmed by lower layers of the UE, andin case that the successful delivery of the first PDCP SN gap report is not confirmed by the lower layers of the UE, transmit, to a target base station, a second PDCP SN gap report including discard information for at least one PDCP service data unit (SDU) indicated as discarded in the first PDCP SN gap report.10.The UE of claim 9,wherein the second PDCP SN gap report further includes discard information for at least one newly discarded PDCP SDU.11.The UE of claim 9,wherein the first PDCP SN gap report is identified as having been transmitted prior to re-establishment of the transmitting PDCP entity.12.The UE of claim 9,wherein the first PDCP SN gap report is identified as having been transmitted within a predetermined time interval before reception of a radio resource control (RRC) reconfiguration message, andwherein the predetermined time interval is 1 second.13.The UE of claim 9,wherein the first PDCP SN gap report is identified as having been transmitted after reception of a radio resource control (RRC) reconfiguration message,wherein the RRC reconfiguration message is applied due to a conditional reconfiguration execution, andwherein the transmission of the second PDCP SN gap report includes submitting or resubmitting the first PDCP SN gap report, stored in the UE, to the lower layers.14.The UE of claim 9,wherein the transmission of the second PDCP SN gap report includes:setting, by the transmitting PDCP entity, a first discarded COUNT (FDC) field of the second PDCP SN gap report to a smallest COUNT value among COUNT values associated with the at least one PDCP SDU indicated as discarded;allocating, by the transmitting PDCP entity, a discard bitmap field to the second PDCP SN gap report;setting, by the transmitting PDCP entity, bits in the discard bitmap field to '1' for the at least one PDCP SDU indicated as discarded and to '0' for all other PDCP SDUs within a range of the discard bitmap field; andsubmitting, from the transmitting PDCP entity to the lower layers, the second PDCP SN gap report.15.The UE of claim 9,wherein the instructions further cause the UE to receive, from the source base station, a configuration parameter included in a radio resource control (RRC) reconfiguration message, andwherein the configuration parameter indicates that a data radio bearer (DRB) is configured to transmit a PDCP SN gap report to a base station during the mobility operation of the UE.

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