Method and system for recovering suspended data in a split bearer NR leg

Abstract

A method for processing data suspended in a New Radio (NR) leg of a split bearer by a user equipment (UE) is disclosed. The method includes predicting the occurrence of an NR uplink (UL) leg switch; sending a buffer status report (BSR) related to protocol data units (PDUs) in a radio link control (RLC) layer and a media access control (MAC) layer in the NR leg based on the predicted occurrence of the NR UL leg switch; and initiating recovery of the suspended PDUs in the NR leg after the NR UL leg switch occurs, wherein the recovery includes sending the suspended PDUs to the Long Term Evolution (LTE) leg of the split bearer.

Description

Technical Field

[0001] Embodiments herein relate to uplink (UL) leg switching in a split bearer network, and more particularly, to methods and systems for enabling recovery of data hanging in a Long Term Evolution (LTE) UL leg or a New Radio (NR) UL leg due to UL leg switching. Background Art

[0002] In a split bearer network, there is a possibility that an uplink (UL) branch switch may be triggered by the network to switch the UL transmission performed by a user equipment (UE). The network may trigger a UL branch switch for a Long Term Evolution (LTE) UL branch or a New Radio (NR) UL branch. When the UL branch switch is triggered, if the UL data sent by the UE exceeds the ul-DataSplitThreshold configured by the network, the network may stop or resume the allocation of UL grants on either of the UL branches (LTE or NR). For example, if the network intends to trigger a UL branch switch from NR to LTE due to poor channel conditions in the NR channel, and if the amount of UL data sent has exceeded the ul-DataSplitThreshold, the network may stop providing UL grants to the user equipment (UE) on the NR UL branch. This may result in all packets in the NR UL branch hanging in the NR UL branch, which packets have been sent by the Packet Data Convergence Protocol (PDCP) layer to the Radio Link Control (RLC) and Medium Access Control (MAC) layers of NR. Furthermore, if the PDCP discard timer expires, the UE may discard packets, which may result in data loss and throughput degradation.

[0003] If the network stops providing UL grants in the NR leg of the split bearer due to UL leg switching, the UE can send a Scheduling Request (SR) to obtain an UL grant from the network. The SR is sent in order to send a Buffer Status Report (BSR), which takes into account PDCP, RLC, and MAC Protocol Data Units (PDUs). If the network does not provide any UL grants on the NR leg, the UE can trigger the NR Random Access Channel (RACH) after the UE has sent the maximum possible number of SRs. This may lead to Radio Link Failure (RLF).

[0004] Due to fluctuating network conditions, if the network continues to change (increase / decrease) the allocation of UL grants between the two legs, PDCP sequence number gaps may be encountered during UL transmission. Fluctuating network conditions also lead to frequent suspension of data in the LTE / NR uplink. Frequent suspension of data leads to a decrease in UL throughput.

[0005] If the network does not allocate the required number of UL grants before the UL leg switching, the UE attempts to clear the PDUs in the NR leg (i.e., NR RLC and NR MAC). The UE sends a BSR that includes PDCP PDUs, RLC PDUs, and MAC PDUs. This may result in hanging data because as long as the UE has UL grants on the NR leg, PDCP may continue to send data to NR RLC and NR MAC, regardless of the number of UL grants available to the UE.

[0006] Figure 1 Depicts an example scenario where UL grant allocation in the NR leg is suspended due to UL leg switching. Currently, the network uses RRC signaling to send parameters related to UL leg switching. The network configures the ul-datasplitthreshold in the radio resource control (RRC) reconfiguration message. When the UL data volume crosses the ul-datasplitthreshold, the UE can send UL data on the master cell group (MCG) leg (LTE), the SCG leg (NR), or both the MCG and SCG legs based on the UL grant. If the UL channel condition of NR deteriorates, the network can switch the UL data path by suspending the allocation of UL grants on NR and providing UL grants on LTE. Once the NR channel condition recovers, the network can resume allocating UL grants on the NR leg.

[0007] Figure 2 This article describes an example scenario where data suspension occurs in the NR leg due to poor NR UL channel conditions. If the network configures NR as the primary UL path, the NR PDCP can push UL data to the NR RLC leg. The NR MAC entity can push data in the UL based on the UL grants available to the UE. If the amount of transmitted UL data reaches the ul-DataSplitThreshold configured by the network and the NR UL channel conditions are suboptimal, the network can suspend providing UL grants on the NR leg and instead provide UL grants on the LTE leg.

[0008] When no UL grant is available and the UE does not receive any grant on the NR leg, PDUs already sent from NR PDCP to NR RLC will be placed in a pending state because there is no means available to send the PDUs that were pushed to NR RLC without an UL grant. PDUs in the pending state must be discarded, resulting in data loss and throughput degradation. If the NR UL channel conditions fluctuate rapidly due to transmitter power limitations, obstacles, phasor angle mismatches, etc., the throughput loss is likely to increase.

[0009] If the UE does not have an UL grant to send a BSR on the NR leg for sending a PDU that has been submitted to the NR RLC, the UE may send a Scheduling Request (SR) to the network to obtain an UL grant. The SR is sent to the network to send the BSR. The UE continues to trigger SRs until the UE obtains the UL grant required to send a BSR to clear the pending data on the NR leg. If the number of SRs triggered by the UE reaches the maximum value configured by the network, the UE may declare an NR Radio Link Failure (RLF) or SCG failure and perform a RACH on the NR. This may result in a disconnection of the NR link.

[0010] Figure 3 Depicted is an example scenario where a gap in PDCP sequence number (SN) is encountered due to an interruption in the continuous data flow. Gaps in PDCP SNs are encountered due to data hanging in the NR leg. Consider that out of "x+y" PDUs sent by NR PDCP to NR RLC, "x" PDUs have already been sent over the NR leg. If the NR UL leg switch occurs after "x" PDUs are sent, there will be no UL grant available in the NR leg. As a result, "y" PDUs will be hanging in the NR leg. When "y" PDUs are received, there is a high probability that an SN gap will be created at the receiver side because after the UL leg switch, PDUs with SN starting from "x+y+1" will be sent over the LTE RLC using UL grant.

[0011] For example, consider that an UL grant is received on the NR RLC and NR PDCP sends PDUs with SNs "x" to "x+50". Consider that PDUs with SNs "x" to "x+25" have been sent and PDUs with SNs "x+26" to "x+50" are in the buffer. At this stage, consider that an UL branch handover is triggered. The network stops allocating NR grants and allocates an LTE UL grant. PDCP sends PDUs with SNs "x+51" to "x+100" via LTE RLC, which are received by the network. Since the network does not receive the PDUs with SNs "x+26" to "x+50", the PDUs with SNs "x+26" to "x+50" create an SN gap on the network side.

[0012] Figure 4 Depicts an example of PDU hanging caused by UL leg switching back and forth between LTE leg and NR leg. Figure 4As shown in the figure, consider that an UL grant is received on the NR leg and PDCP pushes 200 PDUs to the NR RLC and NR MAC, of ​​which 100 PDUs are transmitted. The remaining 100 PDUs will be in the NR RLC and NR MAC. At this stage, consider that the UL leg switch has occurred and the UL grant for transmission is received over the LTE leg. As a result, 100 PDUs will be hanging in the NR buffer.

[0013] Consider that PDCP pushes 100 PDUs to the LTE RLC and LTE MAC, and an UL leg handover occurs after 60 PDUs have been sent. As a result, 40 PDUs will be hanging in the LTE RLC and LTE MAC. Once the UL leg handover occurs, an UL grant for transmission is received over the NR leg.

[0014] Consider that PDCP pushes 200 PDUs to NR RLC and NR MAC, and an UL leg handover occurs after 130 packets have been sent. As a result, 70 PDUs will hang in the NR RLC and NR MAC, unprocessed or unattended. At this stage, an UL grant for transmission is received over the LTE leg. Summary of the Invention

[0015] Technical issues

[0016] A primary objective of the embodiments herein is to disclose a method and system for enabling recovery of data by a User Equipment (UE) with a split bearer configuration, which data is suspended in a New Radio (NR) UL leg due to a network-triggered UL leg handover, wherein the UE is connected to the network.

[0017] Another object of the embodiments herein is to enable a UE to predict NR UL branch switching by determining whether the number of UL grants allocated to the UE for transmitting UL data via the NR branch is less than a predetermined threshold UL grant number for more than a predetermined threshold duration, and whether the number of UL retransmissions is greater than a predetermined threshold UL retransmission number during the predetermined threshold duration.

[0018] Another object of embodiments herein is to perform recovery of protocol data units (PDUs) hanging in an NR buffer when it is predicted that the network is likely to trigger an UL leg handover, wherein the recovery is performed by sending the PDUs to a Long Term Evolution (LTE) Radio Link Control (RLC) and an LTE Medium Access Control (MAC).

[0019] Another object of the embodiments herein is to prevent duplication of PDUs by allowing the UE to delete the PDUs from the LTE RLC and LTE MAC if it is determined that the PDUs have been sent from the LTE RLC and LTE MAC or NRRLC and NR MAC respectively.

[0020] Another object of the embodiments herein is to prevent the Packet Data Convergence Protocol (PDCP) layer from pushing PDUs to the NR RLC and NR MAC after detecting that the network has triggered an NR UL leg handover, and to allow the UE to send a BSR including only the NR RLC PDUs and NR MAC PDUs hanging in the NR buffer in order to clear the NR buffer.

[0021] Another object of embodiments herein is to prevent the UE from triggering a scheduling request (SR) if the NR leg does not have any UL grant and the LTE leg has a UL grant.

[0022] Another object of the embodiments herein is to enable a network to send an indication to a UE regarding a network-triggered NR UL leg switch, wherein the indication is sent via a MAC Control Element (CE) subheader, wherein the UE can determine that the network will trigger an UL leg switch on an NR leg upon receipt of the indication, wherein a MAC CE indicator with / without timing information can be defined.

[0023] Another object of the embodiments herein is to enable recovery of PDUs hanging in the NR buffer by enabling the network to trigger a PDCP status report, wherein the generation of the PDCP status report is triggered by the network if a separate dedicated radio bearer (DRB) is configured in acknowledged mode (AM).

[0024] Technical Solution

[0025] Accordingly, embodiments provide methods and systems for enabling recovery of data that is pending in a new radio (NR) leg due to a network-triggered NR uplink (UL) leg switch. Embodiments allow a user equipment (UE) to recover pending data in an NR UL leg after the network triggers the NR UL leg switch. Embodiments enable the UE to predict the likelihood of a network-triggered NR UL leg switch by identifying whether the number of UL grants allocated to the UE for transmission over the NR leg is less than a predetermined threshold for a duration exceeding a predetermined threshold, and whether the number of UL retransmissions within the predetermined threshold duration is greater than a predetermined threshold number of UL retransmissions.

[0026] Embodiments include preventing the Packet Data Convergence Protocol (PDCP) layer from pushing protocol data units (PDUs) to the NR Radio Link Control (RLC) and NR Media Access Control (MAC) after predicting that the network has triggered an NR UL leg handover. Embodiments herein allow the UE to send a BSR including NR RLC PDUs and NR MAC PDUs hanging in the NR leg in order to clear the NR buffer. Embodiments herein allow PDUs hanging in the NR buffer to be recovered by sending the PDUs to the Long Term Evolution (LTE) RLC and LTE MAC, respectively, when predicting that the network is likely to trigger an NR UL leg handover. Embodiments herein allow the UE to delete PDUs from the LTE RLC and LTE MAC, respectively, if the PDUs have already been sent from the LTE RLC and LTE MAC, or the NR RLC and NR MAC, respectively, to avoid duplication of PDUs.

[0027] These embodiments enable the network to send an indication to the UE regarding the network triggering an NR UL branch switch. The indication may be sent to the UE using a MAC Control Element (CE) subheader. These embodiments enable the UE to determine whether the network will trigger an NR UL branch switch on an NR branch upon receipt of the indication. The network may define a MAC CE indicator with / without timing information. If the network defines a MAC CE indicator without timing information, the UE may determine that the network has triggered an NR UL branch switch upon receipt of the MAC CE indicator. If the network defines a MAC CE indicator with timing information, the UE may determine that the network will trigger an NR UL branch switch after a certain time period upon receipt of the MAC CE indicator.

[0028] Embodiments herein enable recovery of PDUs hanging in an NR buffer by enabling the network to trigger a PDCP status report, wherein the PDCP status report is generated by the network if it is determined that a separate dedicated radio bearer (DRB) is configured in acknowledged mode (AM).

[0029] These and other aspects of the embodiments herein will be better understood and appreciated when considered in conjunction with the following description and accompanying drawings. However, it should be understood that the following description, while indicating embodiments and many specific details therein, is provided by way of illustration and not limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The embodiments of the present invention are shown in the accompanying drawings. Throughout the drawings, the same reference numerals represent corresponding parts in the various figures. With reference to the accompanying drawings, the embodiments of the present invention will be better understood from the following description, in which:

[0031] Figure 1 Depicts an example scenario where UL grant allocation in an NR leg is suspended due to UL leg switching;

[0032] Figure 2 Describes an example scenario where UL data hanging occurs in the NR leg due to poor conditions of the NR UL channel;

[0033] Figure 3 Depicts an example scenario of encountering a gap in Packet Data Convergence Protocol (PDCP) Sequence Numbers (SNs) due to a break in a continuous data flow;

[0034] Figure 4 Depicts an example of protocol data unit (PDU) hanging caused by UL leg switching back and forth on a Long Term Evolution (LTE) leg and an NR leg;

[0035] Figure 5 Depicted is a system including a UE and a network 506 according to embodiments disclosed herein, wherein a user equipment (UE) is configured to predict the occurrence of a network-triggered UL leg handover;

[0036] Figure 6 Depicts a timeline according to an embodiment disclosed herein, in which a UE initiates a procedure for recovering PDUs hanging in an NR UL leg after predicting the possibility of a network-triggered UL leg handover;

[0037] Figure 7 Depicts a timeline according to an embodiment disclosed herein, in which, after predicting the possibility of a network-triggered UL leg handover, the UE initiates another procedure for recovering PDUs hanging in the NR UL leg;

[0038] Figure 8A and Figure 8B Depicting that the network utilizes a medium access control (MAC) control element (CE) to notify the UE about the triggering of an UL leg switch according to embodiments disclosed herein;

[0039] Figure 9 is a flowchart illustrating a method for implementing recovery of data hanging in an NR UL leg due to network-triggered NR UL leg switching according to an embodiment disclosed herein; and

[0040] Figure 10 is a flow chart illustrating another method for implementing recovery of data hanging in an NR UL leg due to a network-triggered UL leg switching according to an embodiment disclosed herein. DETAILED DESCRIPTION

[0041] Before proceeding with the following detailed description, it may be helpful to set forth definitions of certain words and phrases used throughout this patent document: the terms "include" and "comprising" and their derivatives mean inclusion without limitation; the term "or" is inclusive, meaning and / or; the phrases "associated with" and "associated therewith" and their derivatives may mean including, being included, interconnected with, containing, being contained within, connected with, coupled with, communicable with, cooperating with, interleaved, juxtaposed, proximate to, combined with, having, having the property of, and the like; and the term "controller" refers to any device, system, or portion thereof that controls at least one operation, such device being implemented in hardware, firmware, or software, or some combination of at least two. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely.

[0042] In addition, the various functions described below can be implemented or supported by one or more computer programs, each of which is formed of computer-readable program code and embodied in a computer-readable medium. The terms "application" and "program" refer to one or more computer programs, software components, instruction sets, processes, functions, objects, classes, instances, related data, or a portion thereof suitable for implementation with a suitable computer-readable program code. The phrase "computer-readable program code" includes any type of computer code, including source code, object code, and executable code. The phrase "computer-readable medium" includes any type of medium that can be accessed by a computer, such as a read-only memory (ROM), random access memory (RAM), a hard drive, a compact disc (CD), a digital video disc (DVD), or any other type of memory. "Non-transitory" computer-readable media does not include wired, wireless, optical, or other communication links that transmit temporary electrical or other signals. Non-transitory computer-readable media include media that can permanently store data and media that can store data and overwrite it later (such as rewritable optical discs or erasable memory devices).

[0043] Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.

[0044] Discussed below Figures 1 to 10 The various embodiments used to describe the principles of the present disclosure in this patent document are merely exemplary and should not be interpreted in any way as limiting the scope of the present disclosure. Those skilled in the art will understand that the principles of the present disclosure can be implemented in any suitably arranged system or device.

[0045] The embodiments of this invention and their various features and advantageous details are explained more fully with reference to the non-limiting embodiments shown in the accompanying drawings and described in detail in the following description. Descriptions of well-known components and processing technologies are omitted so as not to unnecessarily obscure the embodiments of this invention. The examples used herein are merely for the purpose of facilitating understanding of the manner in which the embodiments of this invention may be practiced and also to enable those skilled in the art to practice the embodiments of this invention. Accordingly, these examples should not be construed as limiting the scope of the embodiments of this invention.

[0046] Embodiments herein disclose methods and systems for enabling recovery of data suspended in a New Radio (NR) leg due to a network-triggered NR uplink (UL) leg handover. Embodiments provide both user equipment (UE) and network-based solutions for recovering suspended data.

[0047] Referring now to the drawings, and more particularly to the Figures 5 to 10 , wherein like reference numerals indicate corresponding features throughout the several views, there is shown a preferred embodiment.

[0048] Figure 5 A system 500 including a UE 501 and a network 506 is depicted according to embodiments disclosed herein, wherein the UE 501 is configured to anticipate the occurrence of an UL branch handover triggered by the network 506. Consider that the UE 501 is connected to the network 506. In one embodiment, the network 506 may include an evolved Node B (eNB) and an evolved packet core (EPC) or a next generation Node B (gNB) and a next generation core (NGC). Consider that the UE 501 operates in a split bearer configuration. Figure 5 As shown, UE 501 includes a processor 502, a communication interface 503, a memory 504, and a display 505. Processor 502 has artificial intelligence (AI) capabilities. UE 501 can transmit UL data and receive downlink (DL) data via a long-term evolution (LTE) leg, a NR leg, or both a LTE leg and a NR leg.

[0049] Consider that UE 501 sends UL data to network 506 using an NR branch. UE 501 can send UL packets through NR radio link control (RLC) and NR medium access control (MAC). UE 501 can send UL data to network 506 using an NR UL grant that has been allocated to UE 501 by network 506. If network 506 detects that the NR channel condition is non-optimal, suboptimal, or poor, network 506 is likely to suspend the allocation of UL grants and trigger NR UL branch switching. Therefore, if UE 501 can detect the condition of the NR channel and determines that the condition of the NR channel is deteriorating; then UE 501 can predict that network 506 is likely to trigger NR UL branch switching.

[0050] If the UE 501 does not receive an NR UL grant, or if the number of NR UL grants available to the UE 501 is insufficient to send all protocol data units (PDUs) in the NR RLC and NR MAC, the PDUs will be hanging in the NR leg. If the Packet Data Convergence Protocol (PDCP) layer continues to push PDUs to the NR RLC and NR MAC, the number of PDUs hanging in the NR leg increases.

[0051] To prevent data hanging due to UL branch switching, embodiments enable UE 501 to predict the possibility of network 506 triggering UL branch switching. Network 506 can trigger UL branch switching when the UL channel condition of the NR branch currently transmitting UL data begins to deteriorate. UE 501 can identify the deterioration of the NR UL branch based on multiple factors through processor 502. Example factors that allow UE 501 to identify the deterioration of the NR UL channel include, but are not limited to, transmit power, modulation and coding scheme (MCS), reference signal received power (RSRP), beam RSRP (RSRP), signal-to-noise ratio (SNR), UL retransmission, path loss, and PDCP discard timer.

[0052] If the power used by the UE 501 to send PDUs is close to the maximum transmit power limit (MTPL) value, the UL MCS value decreases, the number of UL retransmissions is increasing, the reference signal received power (RSRP) is low, the beam RSRP (RSRP) is low, the signal-to-noise ratio (SNR) is poor, the number of UL transmissions at MTPL is greater than a threshold UL transmission number, the PDCP discard timer is activated (if PDUs in the RLC and MAC layers are not transmitted, then after the PDCP discard timer is activated), etc., the processor 502 can determine that the NR channel is deteriorating.

[0053] The processor 502 may check details related to the network 506, such as a public land mobile network (PLMN) identity (ID), a cell ID, a location ID, etc. If the processor 502 has previously determined that the condition of the NR channel is poor in a specific cell and / or location, which is a specific PLMN, the processor 502 may check whether the UE 501 is utilizing services from the specific cell, location, and PLMN. Based on the processor 502's determination that the condition of the NR UL leg is deteriorating, the processor 502 may predict the possibility that the network 506 will trigger an NR UL leg handover.

[0054] Processor 502 may predict a time instance of a likelihood that network 506 will trigger an UL branch handover based on multiple parameters. Processor 502 includes a learning module 502a that may provide values ​​of the multiple parameters as output. Learning module 502a may determine the values ​​of the multiple parameters based on multiple factors, which are inputs to learning module 502a. The multiple parameters include a threshold number of UL grants available to UE 501, a threshold time period during which the number of UL grants available to UE 501 is less than the threshold number of UL grants, a threshold number of retransmissions within the threshold time period, a threshold number of UL transmissions under MTPL, and a threshold time period after which a PDCP discard timer will be activated. As the input values ​​of the multiple factors change, the output values ​​of the multiple parameters are likely to change.

[0055] For example, learning module 502a determines, based on multiple factors, a threshold number of UL grants available to UE 501, a threshold time period during which the number of UL grants available to UE 501 is less than the threshold number of UL grants, a threshold number of retransmissions within the threshold time period, a threshold number of UL transmissions at the medium-term transmission pass (MTPL), and a threshold time period after which the PDCP discard timer will be activated. Processor 502 may predict that network 506 is likely to trigger a UL branch handover at a specific time instance if at least one condition is satisfied: the number of UL grants available to UE 501 for UL transmission is less than the threshold number of UL grants; the time interval during which the number of UL grants available to UE 501 for UL transmission is less than the threshold number of UL grants is greater than the threshold time period; the number of retransmissions within the threshold time period is greater than the threshold number of retransmissions; the number of UL transmissions at the medium-term transmission pass (MTPL) is greater than the threshold number of UL transmissions at the medium-term transmission pass (MTPL); and the time period after which the PDCP discard timer is activated is less than the threshold time period after which the PDCP discard timer should be activated.

[0056] Furthermore, the learning module 502a can update the values ​​of the multiple parameters based on the actual instance of triggering the UL leg handover. If the prediction is inaccurate, i.e., the actual instance of the network 506 triggering the UL leg handover occurs before or after the predicted instance of triggering the UL leg handover, the learning module 502a can update the values ​​of the multiple parameters. In one embodiment, the learning module 502a can utilize a cost function to minimize the difference between the actual time instance and the predicted time instance of the network 506 triggering the UL leg handover and update the values ​​of the multiple parameters.

[0057] For example, if a UL branch handover has occurred, and if the number of UL grants available for UL transmission by UE 501 is greater than a threshold number of UL grants; if the time interval during which the number of UL grants available for UL transmission by UE 501 is less than the threshold number of UL grants is less than a threshold time period; and if the number of retransmissions within the threshold time period is less than a threshold number of retransmissions, then the learning module 502a may update the values ​​of the plurality of parameters. In this case, when a UL branch handover is triggered, the threshold number of UL grants is updated to the number of UL grants available to UE 501; the threshold time period is reduced to a time period during which the number of UL grants available to UE 501 is equal to the updated threshold number of UL grants; and the threshold number of retransmissions is reduced from the earlier value of the threshold number of retransmissions.

[0058] Figure 5 Exemplary units of system 500 are shown, but it should be understood that other embodiments are not limited thereto. In other embodiments, system 500 may include fewer or greater numbers of units. Furthermore, the labels or names of the units of system 500 are for illustrative purposes only and do not limit the scope of the present invention. One or more units may be combined to perform the same or substantially similar functions in system 500.

[0059] Figure 6 A timeline is depicted according to an embodiment disclosed herein, in which, after predicting the possibility of the network 506 triggering an UL branch handover, the UE 501 initiates a process for recovering PDUs hanging in the NR UL branch. Consider that the UE 501 is using the NR branch to send UL data and has determined that the condition of the NR UL branch has deteriorated. The UE 501 can continue to monitor the number of UL grants while the UE is transmitting UL PDUs over the NR branch and whether the ul-DataSplitThreshold has been reached. Once the condition of the NR branch begins to deteriorate, the number of UL grants available to the UE 501 will begin to decrease. If the number of UL grants decreases below a threshold UL grant number (NulTh), the UE 501 can start a threshold timer (T1). Thereafter, the UE 501 can monitor the number of UL retransmissions as the threshold timer increments. After a time period has passed, the threshold timer becomes a default value. The time period specifies a threshold time period for the number of UL grants to decrease below the threshold UL grant number.

[0060] If the processor 502 determines that the number of UL retransmissions within the threshold time period is greater than the threshold number of retransmissions (Nretrans) before the threshold timer expires; or if the number of UL grants is less than the threshold number of UL grants before the threshold timer expires; then the UE 501 can predict that the network is likely to trigger an NR UL branch switch. If the UE 501 predicts that the network 506 is likely to trigger an NR UL branch switch, the processor 502 can be configured to send a buffer status report (BSR) on the NR branch for the NR RLC PDU and the NR MAC PDU. The processor 502 can be configured not to include the NR PDCP PDU in the BSR. Thereafter, the NR PDCP will not push more PDUs to the NR RLC. Through this process (including the NR RLC PDU and the NR MAC PDU in the BSR), the UE 501 attempts to send PDUs to the NR RLC and NR MAC before the network 506 triggers the UL branch switch as predicted.

[0061] If, after UL leg switching is triggered, UE 501 fails to obtain any UL grant on the NR leg and receives an UL grant on the LTE leg, processor 502 may initiate UL transmission on the LTE leg. Processor 502 discards the NR RLC PDUs and NR MAC PDUs in the NR leg that have not yet been sent to network 506. Processor 502 may transmit the discarded NR RLC PDUs and NR MAC PDUs from the NR leg on the LTE leg. In this way, UE 501 can recover pending data without data loss.

[0062] Figure 7A timeline is depicted according to an embodiment disclosed herein, in which, after predicting the likelihood of network 506 triggering an UL leg handover, UE 501 initiates another process for recovering PDUs suspended in an NR UL leg. Consider that UE 501 is sending UL data using an NR leg and has determined that the condition of the NR UL leg has deteriorated. If, before a threshold timer expires, processor 502 determines that the number of UL retransmissions within a threshold period is greater than a threshold number of retransmissions (Nretrans) (the threshold timer expires after a threshold period, where the threshold period specifies a period during which the number of UL grants decreases below a threshold number of UL grants); or if, before the threshold timer expires, the number of UL grants is below a threshold number of UL grants; then UE 501 predicts that network 506 is likely to trigger an NR UL leg handover. Thereafter, processor 502 is configured to create copies of NR RLC PDUs and send these copies to the LTE RLC leg. Similarly, processor 502 is configured to create copies of NR MAC PDUs and send these copies to the LTE MAC leg.

[0063] Once the NR RLC PDU and NR MAC PDU have been sent from the LTE leg or the NR leg, processor 502 may mark the NR RLC PDU and NR MAC PDU. Processor 502 may wait to receive an acknowledgment from network 506 to ascertain whether the network 506 has received the PDU. Once UE 501 receives the acknowledgment, if the PDU has been sent from the NR / LTE leg, processor 502 may delete the PDU from the LTE / NR leg. This may prevent PDCP duplication. This will also minimize the expiration of the t-reordering timer at the network. Simultaneously, processor 502 may be configured to send a BSR for the NR RLC PDU and NR MAC PDU if UE 501 predicts that the network 506 is likely to trigger an NR UL leg handover. Processor 502 may be configured not to include the NR PDCP PDU in the BSR. Once an UL leg handover is triggered by the network, UE 501 cannot obtain any UL grants on the NR leg. However, UE 501 is able to receive UL grants on the LTE leg. The processor 502 may initiate UL transmission on the LTE leg, and the PDCP may stop pushing PDUs on the NR leg.

[0064] Figure 8A and Figure 8BThe present invention illustrates a network 506 utilizing a MAC control element (CE) to notify a UE 501 regarding a triggering of an UL branch handover according to an embodiment disclosed herein. The network 506 may use a MAC CE subheader to send an UL branch handover indication to the UE 501. Upon receiving the indication, the UE 501 may determine that the network 506 will trigger an UL branch handover on an LTE branch or an NR branch. In one embodiment, the network 506 may utilize a reserved bit of the MAC CE subheader to indicate to the UE 501 the network 506 triggering of the UL branch handover. In the MAC CE subheader, bits 33 to 46 are reserved. In one example, the network may use bit 33 to indicate to the UE 501 the network 506 triggering of the UL branch handover.

[0065] like Figure 8A As shown, the MAC CE subheader does not include timing information. When the MAC CE subheader is received by the UE 501, the processor 502 can determine that the network 506 has triggered the UL branch handover. The MAC CE subheader includes one octet. In this octet, the first 6 bits will indicate the logical channel ID (LCID) to which the UL branch handover must be applied. The 7th bit can indicate the cell group ID. The cell group ID indicates the branch on which the UL branch is triggered or is to be triggered, i.e., LTE / NR. An example cell group ID is (MCG 0, SCG 1). If LTE is configured as an MCG and NR is configured as an SCG, the cell group ID indicates that the UL branch is triggered on the NR branch. Another example cell group ID is (MCG1, SCG 0). If LTE is configured as an MCG and NR is configured as an SCG, the cell group ID indicates that the UL branch is triggered on the LTE branch. The last bit in the octet is reserved.

[0066] like Figure 8B As shown, the MAC CE subheader includes timing information. When the MAC CE subheader is received by UE 501, processor 502 can determine that network 506 will trigger an UL branch handover after a specific period of time. The MAC CE subheader includes two octets. The first octet is the same as the octet of the MAC CE subheader without timing information. The second octet can include timing information to be applied before the UL branch handover.

[0067] Upon receiving a MAC CE subheader with / without timing information from the network 506, the UE 501 may apply UL branch switching. If the received MAC CE subheader does not include timing information, the UE 501 may discard all PDUs to be transmitted on the UL branch for which the network 506 has triggered UL branch switching. The UE 501 may retransmit the discarded PDU on another UL branch based on the indication provided in the 7th bit of the MAC CE subheader. This results in the recovery of suspended data. The UE 501 avoids initiating a scheduling request (SR) trigger because the UE 501 is notified about the triggering of the UL branch switching. Since multiple SRs are not triggered, NR radio link failure (RLF) due to maximum SR retransmission will not occur, and the loss of NR connection can be prevented.

[0068] If the received MAC CE subheader includes timing information, the processor 502 may prevent new PDUs from being pushed from PDCP to the RLC of the UL branch for which UL branch switching has been triggered upon receiving the MAC CE subheader. The processor 502 may start a timer that is set to expire when the UL branch switching is triggered. The processor 502 may configure the timer based on the timing information. After calculation using information (MAC) about the data to be retransmitted, a BSR is sent to the network 506. The UE 501 may consider hybrid automatic repeat request (HARQ) retransmission data in the HARQ buffer during the BSR calculation. When the timer expires, the PDU to be transmitted on the UL branch on which the UL branch switching has been triggered may be discarded, and the PDU may be retransmitted on another UL branch. The processor 502 may identify the PDU that has been discarded so that the same PDU is not sent again on the other UL branch.

[0069] In one embodiment, after receiving the MAC CE subheader and resuming the pending PDU by retransmitting the PDU via another UL leg (after the UL leg switch has been triggered), UE 501 can send an acknowledgment to network 506 to indicate that the UL leg switch has been properly applied. To provide this indication, UE 501 can use any of the reserved bits of the MAC CE subheader. In one example, UE 501 has used bit 33 of the MAC CE subheader. UE 501 can send the MAC CE subheader to network 506 as an acknowledgment to confirm the UL leg switch.

[0070] In one embodiment, once an UL leg handover is triggered, the network 506 initiates a process for recovering PDUs that are pending in the UL leg where the UL leg handover has occurred. This process involves triggering a PDCP status report. To recover pending PDUs, the network may trigger a PDCP status report after each UL leg handover. This may be triggered if the split dedicated radio bearer (DRB) is configured in acknowledged mode (AM).

[0071] After the network 506 has sent a MAC CE subheader to the UE 501, a PDCP status report may be triggered to indicate that the network 506 is about to trigger or has already triggered an UL leg handover. If the network 506 has not sent a MAC CE subheader to the UE 501, the PDCP status report may be triggered once the network 506 has decided to trigger an UL leg handover. Once the PDCP status report is generated, the network 506 may send the PDCP status report to the UE 501. If an UL leg handover has been triggered on the NR leg, the UE 501 may identify the PDCP service data units (SDUs) that need to be sent over the LTE UL leg based on the PDCP status report received from the network 506.

[0072] Once the PDCP status report is triggered, the network 506 may compile the PDCP status report by setting the first missing count (FMC) field to RX_DELIV. If RX_DELIV is less than RX_NEXT, a bitmap field may be allocated. The network 506 may set the bitmap field to "0" for all PDCP SDUs that have not yet been received, and optionally for PDCP SDUs for which decompression failed. The network 506 may set the bitmap field to "1" for all PDCP SDUs that have been received by the network 506. Once the UE 501 receives the PDCP status report, the processor 502 may identify the bits set to "1" in the bitmap field, or if the associated COUNT value is less than the value of the FMC field, the processor 502 may discard those PDCP SDUs. The UE 501 may send the remaining SDUs on the LTE UL leg (considering triggering a UL leg handover on the NR leg). This results in lossless data recovery during UL leg handover.

[0073] Figure 9Flowchart 900 illustrates a method for recovering data that is pending in an NR UL leg due to a UL leg handover triggered by the network 506, according to embodiments disclosed herein. At step 901, the method includes predicting the likelihood that the network 506 will trigger an NR UL leg handover. When the UL channel condition of the UL leg begins to deteriorate, the network 506 may trigger the UL leg handover. Embodiments include detecting UL leg deterioration based on multiple factors. Example factors include, but are not limited to, transmit power, MCS value, number of UL retransmissions, RSRP, SNR, path loss, PDCP discard timer, and the like.

[0074] In one embodiment, UE 501 may determine that there is deterioration in the NR UL leg based on at least one condition, including the power used by UE 501 to send PDU being close to MTPL, the UL MCS value decreasing, the number of UL retransmissions increasing, RSRP being low, BRSRP being low, SNR being poor, the number of UL transmissions under MTPL being greater than a threshold UL transmission number, the PDCP discard timer being activated, etc.

[0075] Embodiments include predicting a specific time instance at which network 506 is likely to trigger an UL branch handover based on multiple parameters. Embodiments include determining values ​​for the multiple parameters based on multiple factors. The multiple parameters include a threshold number of UL grants available to UE 501, a threshold time period during which the number of UL grants available to UE 501 is less than a threshold number of UL grants, a threshold number of retransmissions within a threshold time period, a threshold number of UL transmissions under MTPL, and a threshold time period after which a PDCP discard timer will be activated. The values ​​of the multiple parameters are likely to change as the values ​​of the multiple factors change.

[0076] An embodiment includes predicting that a UL branch switch will be triggered by the network 506 at a specific time instance if at least one condition is satisfied. The conditions are: the number of UL grants available for UL transmission by the UE 501 is less than a threshold number of UL grants; the time interval during which the number of UL grants available for UL transmission by the UE 501 is less than the threshold number of UL grants is greater than a threshold time period; the number of retransmissions within the threshold time period is greater than a threshold number of retransmissions; the number of UL transmissions at the MTPL is greater than a threshold number of UL transmissions at the MTPL; and the time period after which the PDCP discard timer is activated is less than a threshold time period after which the PDCP discard timer should be activated.

[0077] At step 902, the method includes preventing the PDCP layer from pushing PDUs to the NR RLC and NR MAC after predicting that the network 506 is likely to trigger an NR UL leg handover. Embodiments herein allow the UE 501 to send a BSR for the NR RLC PDUs and NR MAC PDUs in the NR leg. Embodiments include using an UL grant available to the UE 501 to send the NR RLC PDUs and NR MAC PDUs.

[0078] In one embodiment, after the UE 501 predicts a UL leg switch, a copy of the NR RLC PDU and a copy of the NR MAC PDU are created. The copy of the NR RLC PDU is sent to the LTE RLC leg, and the copy of the NR MAC PDU is sent to the LTE MAC leg. Once the NR RLC PDU and the NR MAC PDU have been sent from the LTE leg or the NR leg, the NR RLC PDU and the NR MAC PDU are marked. An embodiment includes receiving an acknowledgment from the network 506, which allows the UE 501 to ascertain that the network 506 has received the PDU. An embodiment includes deleting the PDU from the LTE leg if the PDU has already been sent from the NR leg. An embodiment includes deleting the PDU from the NR leg if the PDU has already been sent from the LTE leg. This can prevent PDCP duplication.

[0079] At step 903, the method includes initiating recovery of data that was pending in the NR UL leg after the network 506 triggered the NR UL leg handover. Consider that the network 506 has triggered the NR UL leg handover. An embodiment includes sending pending PDUs from the NR RLC and NR MAC to the LTE RLC and LTE MAC after the NR UL leg handover is triggered. However, if the PDUs in the NR RLC and NR MAC are duplicated in the LTE RLC and LTE MAC after the prediction of the UL leg handover, no pending PDUs exist.

[0080] When NR UL leg switching is triggered, UE 501 cannot obtain any UL grant on the NR leg. Instead, UE 501 receives UL grant on the LTE leg. Embodiments allow UE 501 to discard pending PDUs from the NR RLC and NR MAC. After the pending PDUs are discarded from the NR RLC and NR MAC, the pending PDUs are retransmitted from the LTE RLC and LTE MAC to avoid duplication of PDUs.

[0081] If PDUs in the NR RLC and NR MAC are duplicated in the LTE RLC and LTE MAC after prediction of UL leg switch, and if PDUs exist in the NR leg after the NR UL leg switch is triggered, those PDUs in the NR UL leg will be automatically discarded. The duplicates of those PDUs in the LTE UL leg will be retransmitted.

[0082] The various actions in flowchart 900 may be performed in the order presented, in a different order, or simultaneously. In addition, in some embodiments, the Figure 9 Some of the actions listed in .

[0083] Figure 10 Flowchart 1000 illustrates another method for recovering data suspended in an LTE / NR UL leg due to a UL leg handover triggered by network 506, according to embodiments disclosed herein. At step 1001, the method includes receiving an indication from network 506 that network 506 has triggered an LTE / NR UL leg handover or is about to trigger an LTE / NR UL leg handover. Network 506 may send the indication to UE 501 using a MAC CE subheader. In one embodiment, network 506 may use a reserved bit of the MAC CE subheader to send the indication regarding the UL leg handover trigger. Upon receiving the indication via the MAC CE subheader, UE 501 may determine whether network 506 will trigger an LTE / NR UL leg handover on the LTE / NR leg. In one embodiment, network 506 may use bit 7 of the MAC CE subheader to indicate whether the UL leg handover trigger will occur on the LTE leg or the NR leg.

[0084] The network 506 may define a MAC CE subheader with or without timing information. If the network 506 defines a MAC CE subheader without timing information, the UE 501 may determine that the network 506 has triggered an LTE / NR UL branch handover upon receiving the MAC CE subheader. If the network 506 defines a MAC CE subheader with timing information, the UE 501 may determine that the network 506 is about to trigger an LTE / NR UL branch handover upon receiving the MAC CE subheader.

[0085] At step 1002, the method includes initiating a procedure for recovering data suspended in an LTE / NR UL leg due to an LTE / NR UL leg handover. UE 501 may determine whether network 506 has triggered a UL leg handover on an LTE UL leg or an NR UL leg. Considering that a UL leg handover has been triggered by network 506 on an NR UL leg, UE 501 discards all pending PDUs on the NR UL leg if the received MAC CE subheader does not include timing information.

[0086] If the received MAC CE subheader includes timing information, the UE 501 may prevent the new PDU from being pushed from the PDCP to the RLC of the UL leg for which the UL leg switch has been triggered. An embodiment includes starting a timer that expires when the UL leg switch is triggered. The configuration of the timer is based on the timing information. After calculation using information (MAC) about the data to be retransmitted, a BSR is sent to the network 506. The UE 501 considers the HARQ retransmission data in the HARQ buffer during the BSR calculation. The triggering of the UL leg switch on the NR UL leg is considered. Upon expiration of the timer, the PDU on the NR UL leg may be discarded and the PDU may be retransmitted on the LTE leg.

[0087] At step 1003, the method includes sending an acknowledgment by UE 501 to network 506 to indicate that UE 501 has been able to resume the pending data. Once UE 501 is able to resume the pending PDU, after the UL leg handover is triggered, the acknowledgment may be sent to network 506 by retransmitting the PDU via the LTE leg (considering that the UL leg handover has been triggered on the NR UL leg). In one embodiment, UE 501 may use a reserved bit of the MAC CE subheader to send the acknowledgment.

[0088] The various actions in flowchart 1000 may be performed in the order presented, in a different order, or simultaneously. In addition, in some embodiments, the Figure 10 Some of the actions listed in .

[0089] The embodiments disclosed herein may be implemented by at least one software program running on at least one hardware device and performing network management functions to control network elements. Figure 5 The illustrated network elements include blocks that may be implemented as at least one of hardware devices or a combination of hardware devices and software modules.

[0090] The embodiments disclosed herein describe methods and systems for enabling a UE with a split bearer configuration to recover data that is suspended in an LTE UL leg or an NR UL leg due to an UL leg handover triggered by the network to which the UE is connected. Therefore, it should be understood that the scope of protection extends to such a program, and in addition to a computer-readable storage device having a message therein, such a computer-readable storage device contains program code means for implementing one or more steps of the method when the program is executed on a server or mobile device or any suitable programmable device. In a preferred embodiment, the method is implemented by or in conjunction with a software program written in the example Very High Speed ​​Integrated Circuit Hardware Description Language (VHDL) or any other programming language, or by one or more VHDL or several software modules executed on at least one hardware device. The hardware device can be any kind of portable device that can be programmed. The device can also include such a device, which can be, for example, a hardware device (e.g., an application specific integrated circuit (ASIC)), or a combination of hardware and software devices (e.g., an ASIC and a field programmable gate array (FPGA), or at least one microprocessor and at least one memory with a software module therein). The method embodiments described herein can be implemented partially in hardware and partially in software. Alternatively, the invention may be implemented on different hardware devices (eg, using multiple central processing units (CPUs)).

[0091] The foregoing description of specific embodiments will so fully reveal the general nature of the embodiments herein that others may, by applying current knowledge, readily modify and / or adapt such specific embodiments for various applications without departing from the general concepts, and therefore, such adaptations and modifications should and are intended to be understood to be within the meaning and range of equivalents of the disclosed embodiments. It should be understood that the phraseology or terminology used herein is for descriptive purposes only and not for purposes of limitation. Therefore, although the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein may be practiced with modification within the scope of the embodiments described herein.

[0092] Although the present disclosure has been described with various embodiments, various changes and modifications may occur to those skilled in the art. The present disclosure is intended to encompass such changes and modifications as fall within the scope of the appended claims.

Claims

1. A user equipment (UE) for processing data suspended in a New Radio (NR) leg of a split bearer, the UE comprising: Communication interface; as well as a processor coupled to the communication interface, wherein the processor is configured to: Predict the occurrence of NR uplink UL branch switching; Based on the prediction of occurrence of NR UL leg switching, sending a buffer status report (BSR) related to protocol data units (PDUs) in a radio link control (RLC) layer and a media access control (MAC) layer in the NR leg; as well as After the NR UL leg switching occurs, initiating recovery of the suspended PDUs in the NR leg, wherein the recovery comprises sending the suspended PDUs to the Long Term Evolution (LTE) leg of the separated bearer, The occurrence of NR UL branch switching is predicted when at least one of the following items is determined: The number of UL grants allocated to the UE for transmitting UL data through the NR leg is less than a threshold UL grant number for more than a threshold duration; The number of UL retransmissions during the threshold duration is greater than a threshold UL retransmission number; activating a Packet Data Convergence Protocol (PDCP) discard timer after a time period, wherein the time period is less than a threshold activation time period, the PDCP discard timer being activated after the threshold activation time period; and The number of UL transmissions under the maximum transmit power limit MTPL is greater than a threshold number of UL transmissions under the MTPL.

2. The UE according to claim 1, wherein: The threshold duration is a time period spanning the detection of deterioration of the NR leg and the occurrence of the NR UL leg switching.

3. The UE according to claim 1, wherein: The threshold UL grant number, the threshold duration, the threshold UL retransmission number, the threshold activation period of the PDCP discard timer, and the threshold UL transmission number under MTPL are determined based on at least one of the following: UE transmit power, modulation and coding scheme MCS, reference signal received power RSRP, beam RSRP, UL retransmission, path loss, signal-to-noise ratio SNR, PDCP discard timer, cell identity ID, location ID, and public land mobile network PLMN ID.

4. The UE according to claim 3, wherein: The values ​​of the threshold UL grant number, the threshold duration, the threshold UL retransmission number, the threshold activation period of the PDCP discard timer, and the threshold UL transmission number under MTPL are updated based on the accuracy of the prediction of the NR UL leg switch. The UE according to claim 1 , wherein: The processor is configured to prevent a PDCP layer PDU from being included in the BSR, and The processor is further configured to enable the PDCP layer to push the PDCP layer PDU to the LTE branch based on a prediction of the occurrence of the NR UL branch switching. The UE according to claim 1 , wherein: The processor is further configured to retransmit the suspended PDU from the LTE leg after the NR UL leg switch occurs.

7. The UE according to claim 1, wherein: The processor is further configured to: Creating a copy of the PDU in the RLC layer and the MAC layer in the NR leg; Before sending a BSR related to the PDUs in the RLC layer and the MAC layer in the NR leg, sending a copy of the PDU to the LTE leg of the split bearer based on a prediction of occurrence of the NR UL leg switch; After transmitting at least one of the PDUs from one of the LTE leg and the NR leg, marking the at least one PDU; as well as The at least one PDU is deleted from one of the following: the NR leg, if the at least one PDU is sent from the LTE leg; and the LTE leg, if the at least one PDU is sent from the NR leg.

8. The UE according to claim 7, wherein: The processor is configured to: preventing PDCP layer PDUs from being included in the BSR; and Based on the prediction of the occurrence of the NR UL branch switching, the PDCP layer PDU pushes the PDCP layer PDU to the LTE branch.

9. A method for processing data suspended in a New Radio (NR) leg of a separate bearer by a user equipment (UE), the method comprising: Predict the occurrence of NR uplink UL branch switching; Based on the prediction of occurrence of the NR UL leg switch, sending a buffer status report (BSR) related to protocol data units (PDUs) in a radio link control (RLC) layer and a media access control (MAC) layer in the NR leg; as well as After the NR UL leg switching occurs, initiating recovery of the suspended PDUs in the NR leg, wherein the recovery comprises sending the suspended PDUs to the Long Term Evolution (LTE) leg of the separated bearer, The occurrence of NR UL branch switching is predicted when at least one of the following items is determined: The number of UL grants allocated to the UE for transmitting UL data through the NR leg is less than a threshold UL grant number for more than a threshold duration; a number of UL retransmissions during the threshold duration is greater than a threshold number of UL retransmissions; activating a Packet Data Convergence Protocol (PDCP) discard timer after a time period, wherein the time period is less than a threshold activation time period, the PDCP discard timer being activated after the threshold activation time period; and The number of UL transmissions under the maximum transmit power limit MTPL is greater than a threshold number of UL transmissions under the MTPL.

10. The method according to claim 9, wherein: The threshold duration is a time period spanning the detection of deterioration of the NR leg and the occurrence of the NR UL leg switching.

11. The method according to claim 9, wherein: The threshold UL grant number, the threshold duration, the threshold UL retransmission number, the threshold activation period of the PDCP discard timer, and the threshold UL transmission number under MTPL are determined based on at least one of the following: UE transmit power, modulation and coding scheme MCS, reference signal received power RSRP, beam RSRP, UL retransmission, path loss, signal-to-noise ratio SNR, PDCP discard timer, cell identity ID, location ID, and public land mobile network PLMN ID.

12. The method according to claim 11, wherein The values ​​of the threshold UL grant number, the threshold duration, the threshold UL retransmission number, the threshold activation period of the PDCP discard timer, and the threshold UL transmission number under MTPL are updated based on the accuracy of the prediction of the NR UL leg switch.

13. The method according to claim 9, wherein: preventing, by the UE, a PDCP layer PDU from being included in the BSR, and The PDCP layer is enabled by the UE to push the PDCP layer PDU to the LTE branch based on the prediction of the occurrence of the NR UL branch switching.

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