Method and apparatus for switching uplink transmission on a split bearer in the uplink

Abstract

A user equipment (UE) configured for dual connectivity with split bearer configuration can send uplink data packets to one or both of a master cell group (MCG) and a secondary cell group (SCG). The UE can send an uplink transmission from a packet data convergence protocol (PDCP) entity on one or both of a first radio link control (RLC) entity associated with the MCG and a second RLC entity associated with the SCG. The configuration includes a transmit buffer threshold. The UE can receive an uplink handover start indication at the PDCP entity. The UE can activate the second RLC entity in response to receiving the uplink handover start indication. The UE can send a buffer status report based on the current transmit buffer level plus the transmit buffer threshold. Thus, the UE can communicate with the SCG based on the uplink handover start indication.

Description

Technical Field

[0001] Generally speaking, the present disclosure relates to communication systems, and more particularly, the present disclosure relates to methods and apparatuses for switching uplink transmissions on split uplink bearers. Background Art

[0002] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasting. A typical wireless communication system may employ multiple access technologies capable of supporting communication with multiple users by sharing available system resources. Examples of such multiple access technologies include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, Single Carrier Frequency Division Multiple Access (SC-FDMA) systems, and Time Division Synchronous Code Division Multiple Access (TD-SCDMA) systems.

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

[0004] A simplified overview of one or more aspects is given below in order to provide a basic understanding of such aspects. This overview is not an exhaustive review of all expected aspects, and is neither intended to identify key or important elements of all aspects, nor to delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is given later.

[0005] A user equipment (UE) configured for dual connectivity with a split bearer architecture can send uplink data packets to one or both of a master cell group (MCG) and a secondary cell group (SCG). The MCG may become temporarily unavailable (e.g., due to handover or poor channel conditions). Although the UE can send uplink data packets to the SCG, the data packets sent can also accumulate in the buffer of the MCG, resulting in a slower recovery when the MCG becomes available.

[0006] A user equipment (UE) configured for dual connectivity with a split bearer configuration can send uplink data packets to one or both of a master cell group (MCG) and a secondary cell group (SCG). The UE can send an uplink transmission from a packet data convergence protocol (PDCP) entity on one or both of a first radio link control (RLC) entity associated with the MCG and a second RLC entity associated with the SCG. The configuration includes a transmit buffer threshold. The UE can receive an uplink handover start indication at the PDCP entity. The uplink handover start indication can indicate that the MCG may become temporarily unavailable or that use of the SCG is desired. The UE can activate the second RLC entity in response to receiving the uplink handover start indication. The UE can send a buffer status report based on the current transmit buffer level plus the transmit buffer threshold. Thus, the UE can communicate with the SCG instead of the MCG based on the uplink handover start indication. Uplink data packets may not accumulate in the buffer of the MCG, so the radio link with the MCG can recover without additional latency. In some cases, communication with the SCG can provide additional benefits, such as greater bandwidth and lower latency.

[0007] In one aspect of the present disclosure, methods, computer-readable media, and apparatuses are provided. The apparatus can include a memory and at least one processor coupled to the memory. The processor can be configured to: send an uplink transmission from a user equipment using an uplink split bearer configuration from a packet data convergence protocol (PDCP) layer on one or both of a first radio link control (RLC) entity associated with a master cell group (MCG) and a second RLC entity associated with a secondary cell group (SCG), the configuration including a transmit buffer threshold. The processor can be configured to: receive an uplink handover start indication at the PDCP entity. The processor can be configured to: activate the second RLC entity in response to receiving the uplink handover start indication. The processor can be configured to: send a buffer status report based on the current transmit buffer level plus the transmit buffer threshold.

[0008] To achieve the foregoing and related purposes, one or more aspects include the features described fully hereinafter and particularly pointed out in the claims. The following description and the drawings set forth in detail certain illustrative features of one or more aspects. However, these features are indicative of only some of the various ways in which the principles of the various aspects may be employed and the description is intended to include all such aspects and their equivalents. Description of the Drawings

[0009] Figure 1 is a diagram illustrating an example of a wireless communication system and an access network.

[0010] Figure 2A 、 Figure 2B 、 Figure 2C and Figure 2D are diagrams respectively illustrating examples of a first 5G / NR frame, DL channels within a 5G / NR subframe, a second 5G / NR frame, and UL channels within a 5G / NR subframe.

[0011] Figure 3 is a diagram illustrating an example of a base station and a user equipment (UE) in an access network.

[0012] Figure 4 is a diagram illustrating an example of a split bearer architecture for dual connectivity.

[0013] Figure 5 is a diagram illustrating an example transmission using a split bearer architecture for dual connectivity when a transmission path becomes unavailable.

[0014] Figure 6 is a diagram illustrating an example transmission using a split bearer architecture for dual connectivity when a transmission path becomes unavailable and the data volume is greater than the uplink buffer threshold.

[0015] Figure 7 is a diagram illustrating an example transmission using a split bearer architecture for dual connectivity with PDCP duplication when a transmission path becomes unavailable.

[0016] Figure 8 is a diagram illustrating an example of uplink path switching for a split bearer architecture.

[0017] Figure 9 is a message diagram illustrating an example transmission and processing for uplink path switching.

[0018] Figure 10 is a flowchart of a method of wireless communication.

[0019] Figure 11 is a conceptual data flow diagram illustrating the data flow between different units / components in an example device.

[0020] Figure 12 FIG. is an example showing a hardware implementation of an apparatus using a processing system. DETAILED DESCRIPTION

[0021] The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be implemented. For the purpose of providing a thorough understanding of the various concepts, the detailed description includes specific details. It will be apparent, however, to one of ordinary skill in the art that the concepts may be implemented without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

[0022] Certain aspects of the present disclosure are now described with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description by various blocks, components, circuits, processes, algorithms, etc. (collectively referred to as “elements”), and illustrated in the accompanying drawings. These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

[0023] By way of example, an element, or any portion of an element, or any combination of elements may be implemented as a “processing system” that includes one or more processors. Examples of processors include: a microprocessor, a microcontroller, a graphics processing unit (GPU), a central processing unit (CPU), an application processor, a digital signal processor (DSP), a reduced instruction set computing (RISC) processor, a system on a chip (SoC), a baseband processor, a field programmable gate array (FPGA), a programmable logic device (PLD), a state machine, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functions described throughout the present disclosure. One or more processors in the processing system may execute software. Software should be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software components, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, processes, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0024] Accordingly, in one or more example embodiments, the described functionality may be implemented in hardware, software, or any combination thereof. If implemented in software, the functionality may be stored on or encoded as one or more instructions or code on a computer-readable medium. Computer-readable media includes computer storage media. Storage media can be any available media that can be accessed by a computer. By way of example and not limitation, such computer-readable media can include random access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), optical disk storage, magnetic disk storage, other magnetic storage devices, combinations of the foregoing types of computer-readable media, or any other media that can be used to store computer-executable code in the form of instructions or data structures and that can be accessed by a computer.

[0025] Figure 1 FIG. 4 is a diagram illustrating an example of a wireless communication system and an access network 100. The wireless communication system (also referred to as a wireless wide area network (WWAN)) includes a base station 102, a UE 104, an evolved packet core (EPC) 160, and another core network 190 (e.g., a 5G core (5GC)). The base station 102 may include macro cells (high-power cellular base stations) and / or small cells (low-power cellular base stations). Macro cells include base stations. Small cells include femtocells, picocells, and microcells.

[0026] The base stations 102 configured for 4G LTE (collectively referred to as an evolved universal mobile telecommunications system (UMTS) terrestrial radio access network (E-UTRAN)) may be interfaced with the EPC 160 via a backhaul link 132 (e.g., an S1 interface). The base stations 102 configured for 5G NR (collectively referred to as a next-generation RAN (NG-RAN)) may be interfaced with the core network 190 via a backhaul link 184. In addition to other functions, the base station 102 may perform one or more of the following functions: transmission of user data, wireless channel encryption and decryption, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection establishment and release, load balancing, distribution of non-access stratum (NAS) messages, NAS node selection, synchronization, radio access network (RAN) sharing, multimedia broadcast multicast service (MBMS), user and device tracking, radio access network information management (RIM), paging, positioning, and delivery of warning messages. The base stations 102 may communicate with each other directly or indirectly (e.g., via the EPC 160 or the core network 190) via a backhaul link 134 (e.g., an X2 interface). The backhaul link 134 may be wired or wireless.

[0027] Base station 102 can communicate wirelessly with UE 104. Each base station 102 in base station 102 can provide communication coverage for a corresponding geographic coverage area 110. There can be overlapping geographic coverage areas 110. For example, small cell 102' can have a coverage area 110' that overlaps with the coverage areas 110 of one or more macro base stations 102. A network including both small cells and macro cells can be referred to as a heterogeneous network. The heterogeneous network can also include a home evolved Node B (eNB) (HeNB), which can provide services to a restricted group called a closed subscriber group (CSG). The communication link 120 between base station 102 and UE 104 can include an uplink (UL) (also referred to as a reverse link) transmission from UE 104 to base station 102 and / or a downlink (DL) (also referred to as a forward link) transmission from base station 102 to UE 104. The communication link 120 can use multiple-input multiple-output (MIMO) antenna technology, which includes spatial multiplexing, beamforming, and / or transmit diversity. The communication link can be over one or more carriers. Base station 102 / UE 104 can use a spectrum of up to a total of Yx MHz (x component carriers) in carrier aggregation allocated for transmission in each direction, with each carrier having a bandwidth of up to Y MHz (e.g., 5, 10, 15, 20, 100, 400, etc. MHz). The carriers can be adjacent to each other or can be non-adjacent to each other. The allocation of carriers can be asymmetric with respect to DL and UL (e.g., more or fewer carriers can be allocated for DL compared to UL). The component carriers can include a primary component carrier and one or more secondary component carriers. The primary component carrier can be referred to as the primary cell (PCell), and the secondary component carriers can be referred to as secondary cells (SCell).

[0028] Certain UEs 104 can communicate with each other using device-to-device (D2D) communication link 158. The D2D communication link 158 can use DL / UL WWAN spectrum. The D2D communication link 158 can use one or more sidelink channels, such as the physical sidelink broadcast channel (PSBCH), the physical sidelink discovery channel (PSDCH), the physical sidelink shared channel (PSSCH), and the physical sidelink control channel (PSCCH). D2D communication can be through a variety of wireless D2D communication systems, such as, for example, FlashLinQ, WiMedia, Bluetooth, ZigBee, Wi-Fi based on the IEEE 802.11 standard, LTE, or NR.

[0029] The wireless communication system may further include a Wi-Fi access point (AP) 150 that communicates with a Wi-Fi station (STA) 152 via a communication link 154 in the 5 GHz unlicensed spectrum. When communicating in the unlicensed spectrum, the STA 152 / AP 150 may perform a Clear Channel Assessment (CCA) before communicating to determine whether the channel is available.

[0030] The small cell 102' may operate in licensed and / or unlicensed spectrum. When operating in the unlicensed spectrum, the small cell 102' may employ NR and use the same 5 GHz unlicensed spectrum as that used by the Wi-Fi AP 150. The small cell 102' employing NR in the unlicensed spectrum may enhance coverage and / or increase the capacity of the access network.

[0031] The base station 102 (whether a small cell 102' or a large cell (e.g., a macro base station)) may include an eNB, a gNodeB (gNB), or another type of base station. Some base stations (such as the gNB 180) may operate in the traditional sub 6 GHz spectrum, at millimeter wave (mmW) frequencies, and / or near mmW frequencies to communicate with the UE 104. When the gNB 180 operates at mmW or near mmW frequencies, the gNB 180 may be referred to as a mmW base station. The Extremely High Frequency (EHF) is a part of the RF in the electromagnetic spectrum. The EHF has a range of 30 GHz to 300 GHz and a wavelength between 1 millimeter and 10 millimeters. The radio waves in this band may be referred to as millimeter waves. Near mmW may extend down to a frequency of 3 GHz, having a wavelength of 100 millimeters. The Super High Frequency (SHF) band extends between 3 GHz and 30 GHz and is also referred to as centimeter waves. Communication using the mmW / near mmW radio frequency band (e.g., 3 GHz–300 GHz) has extremely high path loss and short distances. The mmW base station 180 may utilize beamforming 182 with the UE 104 to compensate for the extremely high path loss and short distances.

[0032] Base station 180 may transmit beamformed signals to UE 104 in one or more transmission directions 182'. UE 104 may receive beamformed signals from base station 180 in one or more reception directions 182". UE 104 may also transmit beamformed signals to base station 180 in one or more transmission directions. Base station 180 may receive beamformed signals from UE 104 in one or more reception directions. Base station 180 / UE 104 may perform beam training to determine the optimal reception and transmission directions for each of base station 180 / UE 104. The transmission and reception directions of base station 180 may be the same or may be different. The transmission and reception directions of UE 104 may be the same or may be different.

[0033] EPC 160 may include a Mobility Management Entity (MME) 162, other MMEs 164, Serving Gateway 166, Multimedia Broadcast Multicast Service (MBMS) Gateway 168, Broadcast Multicast Service Center (BM-SC) 170, and Packet Data Network (PDN) Gateway 172. MME 162 may communicate with a Home Subscriber Server (HSS) 174. MME 162 is a control node that processes signaling between UE 104 and EPC 160. Generally, MME 162 provides bearer and connection management. All user Internet Protocol (IP) packets are transmitted through Serving Gateway 166, which itself is connected to PDN Gateway 172. PDN Gateway 172 provides IP address allocation to the UE and other functions. PDN Gateway 172 and BM-SC 170 are connected to IP services 176. IP services 176 may include the Internet, intranet, IP Multimedia Subsystem (IMS), PS streaming services, and / or other IP services. BM-SC 170 may provide functions for MBMS user service provisioning and delivery. BM-SC 170 may act as an entry point for content provider MBMS transmissions, may be used to authorize and initiate MBMS bearer services within a Public Land Mobile Network (PLMN), and may be used to schedule MBMS transmissions. MBMS Gateway 168 may be used to distribute MBMS traffic to base stations 102 belonging to a Multicast Broadcast Single Frequency Network (MBSFN) area for a particular broadcast service, and may be responsible for session management (start / stop) and collecting charging information related to eMBMS.

[0034] The core network 190 may include an Access and Mobility Management Function (AMF) 192, other AMFs 193, a Session Management Function (SMF) 194, and a User Plane Function (UPF) 195. The AMF 192 may communicate with a Unified Data Management (UDM) 196. The AMF 192 is a control node that processes signaling between the UE 104 and the core network 190. Generally, the AMF 192 provides QoS flow and session management. All user Internet Protocol (IP) packets are transmitted through the UPF 195. The UPF 195 provides IP address allocation to the UE and other functions. The UPF 195 is connected to an IP service 197. The IP service 197 may include the Internet, an intranet, an IP Multimedia Subsystem (IMS), a PS streaming service, and / or other IP services.

[0035] The base station may also be referred to as a gNB, Node B, evolved Node B (eNB), access point, base station transceiver, radio base station, radio transceiver, transceiver function, Basic Service Set (BSS), Extended Service Set (ESS), Transmission and Reception Point (TRP), or some other suitable term. The base station 102 provides an access point to the EPC 160 or the core network 190 for the UE 104. Examples of the UE 104 include cellular phones, smart phones, Session Initiation Protocol (SIP) phones, laptop computers, personal digital assistants (PDAs), satellite radio units, global positioning systems, multimedia devices, video devices, digital audio players (e.g., MP3 players), cameras, gaming devices, tablet devices, smart devices, wearable devices, vehicles, utility meters, gas pumps, large or small kitchen appliances, healthcare devices, implants, sensors / actuators, displays, or any other similar functional devices. Some of the UEs 104 may be referred to as IoT devices (e.g., parking meters, gas pumps, toasters, vehicles, heart monitors, etc.). The UE 104 may also be referred to as a station, mobile station, user station, mobile unit, user unit, radio unit, remote unit, mobile device, radio device, wireless communication device, remote device, mobile user station, access terminal, mobile terminal, wireless terminal, remote terminal, cell phone, user agent, mobile client, client, or some other suitable term.

[0036] Refer again to Figure 1, in some aspects, the UE 104 may include a UL path switching component 140 configured to control the activation of a second radio link control (RLC) entity in a UL split bearer configuration in response to an UL split start / stop indication. For example, the UL path switching component 140 may use an UL split bearer configuration from the packet data convergence protocol (PDCP) layer on one or both of a first radio link control (RLC) entity associated with a master cell group (MCG) and a second RLC entity associated with a secondary cell group (SCG) to send UL transmissions from the UE 104. The UL split bearer configuration may include a transmit buffer threshold. The UL path switching component 140 may receive an UL handover start indication at the PDCP entity. The UL path switching component 140 may activate the second RLC entity in response to receiving the UL handover start indication. The UL path switching component 140 may send a buffer status report based on the current transmit buffer level plus the transmit buffer threshold. Thus, even when the UL transmit buffer level does not meet the transmit buffer threshold, the UL path switching component 140 may enable the UE 104 to use the second RLC entity instead of or in conjunction with the first RLC entity. Doing so may reduce latency and / or increase UL throughput.

[0037] Although the following description may focus on 5G NR, the concepts described herein may be applicable to other similar areas such as LTE, LTE-A, CDMA, GSM, and other wireless technologies.

[0038] Figure 2A FIG. 200 is an example showing a first subframe within a 5G / NR frame structure. Figure 2B FIG. 230 is an example showing DL channels within a 5G / NR subframe. Figure 2C FIG. 250 is an example showing a second subframe within a 5G / NR frame structure. Figure 2D FIG. 280 is an example showing UL channels within a 5G / NR subframe. The 5G / NR frame structure may be FDD (where, for a particular set of subcarriers (carrier system bandwidth), the subframes within that set of subcarriers are dedicated to DL or UL), or may be TDD (where, for a particular set of subcarriers (carrier system bandwidth), the subframes within that set of subcarriers are dedicated to both DL and UL). In Figure 2A , Figure 2CIn the provided example, the 5G / NR frame structure is assumed to be TDD, where subframe 4 is configured with slot format 28 (mostly DL), where D is DL, U is UL, and X is flexibly available between DL / UL, and subframe 3 is configured with slot format 34 (mostly UL). Although subframe 3 and subframe 4 are shown with slot formats 34 and 28 respectively, any particular subframe can be configured with any of the various available slot formats 0 - 61. Slot formats 0 and 1 are all-DL and all-UL respectively. The other slot formats 2 - 61 include a mixture of DL, UL, and flexible symbols. The UE is configured with a slot format by the received Slot Format Indicator (SFI) (dynamically via Downlink Control Information (DCI) or semi-statically / statically via Radio Resource Control (RRC) signaling). Note that the following description also applies to the 5G / NR frame structure as TDD.

[0039] Other wireless communication technologies may have different frame structures and / or different channels. A frame (10 ms) can be divided into 10 equally sized subframes (1 ms). Each subframe can include one or more slots. A subframe can also include mini-slots, which can include 7, 4, or 2 symbols. Each slot can include 7 or 14 symbols, depending on the slot configuration. For slot configuration 0, each slot can include 14 symbols, while for slot configuration 1, each slot can include 7 symbols. Symbols on the DL can be Cyclic Prefix (CP) OFDM (CP - OFDM) symbols. Symbols on the UL can be CP - OFDM symbols (for high throughput scenarios) or Discrete Fourier Transform (DFT) spread OFDM (DFT - s - OFDM) symbols (also known as Single - Carrier Frequency - Division Multiple Access (SC - FDMA) symbols) (for power - limited scenarios; limited to single - stream transmission). The number of slots within a subframe can be based on the slot configuration and numerology. For slot configuration 0, different numerologies μ0 to 5 allow 1, 2, 4, 8, 16, and 32 slots per subframe respectively. For slot configuration 1, different numerologies 0 to 2 allow 2, 4, and 8 slots per subframe respectively. Accordingly, for slot configuration 0 and numerology μ, there are 14 symbols / slot and 2 μ slots / subframe. The subcarrier spacing and symbol length / duration are functions of the numerology. The subcarrier spacing can be equal to 2 μ *15 kHz, where μ is the numerology from 0 to 5. Thus, numerology μ = 0 has a subcarrier spacing of 15 kHz, and numerology μ = 5 has a subcarrier spacing of 480 kHz. The symbol length / duration is inversely related to the subcarrier spacing. Figure 2A - Figure 2DAn example of slot configuration 0 with 14 symbols per time slot and digital scheme μ = 0 with 1 time slot per subframe is provided. The subcarrier spacing is 15 kHz, and the symbol duration is approximately 66.7 μs.

[0040] The resource grid can be used to represent the frame structure. Each time slot includes resource blocks (RBs) (also referred to as physical RBs (PRBs)), which span 12 consecutive subcarriers. The resource grid is divided into multiple resource elements (REs). The number of bits carried by each RE depends on the modulation scheme.

[0041] As Figure 2A shown, some of the REs in the RE carry reference (pilot) signals (RSs) for the UE. The RS can include demodulation RS (DM-RS) for channel estimation at the UE (indicated as Rx for one specific configuration, where 100x is the port number, but other DM-RS configurations are possible) and channel state information reference signal (CSI-RS). The RS can also include beam measurement RS (BRS), beam refinement RS (BRRS), and phase tracking RS (PT-RS).

[0042] Figure 2B Examples of various DL channels within a subframe of a frame are shown. The physical downlink control channel (PDCCH) carries DCI within one or more control channel elements (CCEs), each CCE including nine resource element groups (REGs), each REG including four consecutive REs in one OFDM symbol. The primary synchronization signal (PSS) can be in symbol 2 of a specific subframe of the frame. The PSS is used by the UE104 to determine subframe / symbol timing and the physical layer identity. The secondary synchronization signal (SSS) can be in symbol 4 of a specific subframe of the frame. The SSS is used by the UE to determine the physical layer cell identity group number and the radio frame timing. Based on the physical layer identity and the physical layer cell identity group number, the UE can determine the physical cell identifier (PCI). Based on the PCI, the UE can determine the location of the aforementioned DM-RS. The physical broadcast channel (PBCH) (which carries the master information block (MIB)) can be logically grouped with the PSS and SSS to form a synchronization signal (SS) / PBCH block. The MIB provides the number of RBs in the system bandwidth and the system frame number (SFN). The physical downlink shared channel (PDSCH) carries user data, broadcast system information not sent through the PBCH (such as system information blocks (SIBs)), and paging messages.

[0043] As Figure 2CAs shown, some of the REs in the RE carry DM-RS for channel estimation at the base station (indicated as R for a specific configuration, but other DM-RS configurations are possible). The UE can send DM-RS for the physical uplink control channel (PUCCH) and DM-RS for the physical uplink shared channel (PUSCH). The PUSCH DM-RS can be sent in the one or two symbols preceding the PUSCH. The PUCCH DM-RS can be sent in different configurations depending on whether a short PUCCH or a long PUCCH is sent and depending on the specific PUCCH format used. Although not shown, the UE can send a sounding reference signal (SRS). The SRS can be used by the base station for channel quality estimation to enable frequency-dependent scheduling on the UL.

[0044] Figure 2D Examples of various UL channels within a subframe of a frame are shown. The PUCCH can be located as indicated in one configuration. The PUCCH carries uplink control information (UCI), such as a scheduling request, a channel quality indicator (CQI), a precoding matrix indicator (PMI), a rank indicator (RI), and HARQ ACK / NACK feedback. The PUSCH carries data and can additionally be used to carry a buffer status report (BSR), a power headroom report (PHR), and / or UCI.

[0045] Figure 3It is a block diagram of the communication between the base station 310 and the UE 350 in the access network. In the DL, IP packets from the EPC 160 can be provided to the controller / processor 375. The controller / processor 375 implements layer 3 and layer 2 functions. Layer 3 includes the radio resource control (RRC) layer, and layer 2 includes the service data adaptation protocol (SDAP) layer, the packet data convergence protocol (PDCP) layer, the radio link control (RLC) layer, and the media access control (MAC) layer. The controller / processor 375 provides: RRC layer functions associated with: broadcasting of system information (e.g., MIB, SIB), RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), inter-radio access technology (RAT) mobility, and measurement configuration for UE measurement reporting; PDCP layer functions associated with: header compression / decompression, security (encryption, decryption, integrity protection, integrity verification), and handover support functions; RLC layer functions associated with: transmission of upper layer packet data units (PDUs), error correction via ARQ, concatenation, segmentation, and reassembly of RLC service data units (SDUs), re-segmentation of RLC data PDUs, and re-ordering of RLC data PDUs; and MAC layer functions associated with: mapping between logical channels and transport channels, multiplexing of MAC SDUs onto transport blocks (TBs), demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction via HARQ, priority handling, and logical channel prioritization.

[0046] The transmit (TX) processor 316 and the receive (RX) processor 370 implement layer 1 functions associated with various signal processing functions. Layer 1, which includes the physical (PHY) layer, may include error detection on the transport channel, forward error correction (FEC) encoding / decoding of the transport channel, interleaving, rate matching, mapping to the physical channel, modulation / demodulation of the physical channel, and MIMO antenna processing. The TX processor 316 processes the mapping to the signal constellation based on various modulation schemes (e.g., binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), M-phase shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The encoded and modulated symbols may then be split into parallel streams. Each stream may then be mapped to OFDM subcarriers, multiplexed with reference signals (e.g., pilots) in the time and / or frequency domain, and then combined together using an inverse fast Fourier transform (IFFT) to generate a physical channel carrying a stream of time-domain OFDM symbols. The OFDM stream is space precoded to generate multiple spatial streams. Channel estimates from the channel estimator 374 may be used to determine the encoding and modulation schemes, as well as for spatial processing. The channel estimates may be derived based on reference signals transmitted by the UE 350 and / or channel status feedback. Each spatial stream may then be provided to a different antenna 320 via a separate transmitter 318TX. Each transmitter 318TX may modulate an RF carrier with the corresponding spatial stream for transmission.

[0047] At the UE 350, each receiver 354RX receives signals via its corresponding antenna 352. Each receiver 354RX recovers the information modulated onto the RF carrier and provides the information to the receive (RX) processor 356. The TX processor 368 and the RX processor 356 implement layer 1 functions associated with various signal processing functions. The RX processor 356 may perform spatial processing on the information to recover any spatial streams destined for the UE 350. If multiple spatial streams are destined for the UE 350, they may be combined into a single OFDM symbol stream by the RX processor 356. The RX processor 356 then uses a fast Fourier transform (FFT) to transform the OFDM symbol stream from the time domain to the frequency domain. The frequency-domain signal includes a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols and reference signals on each subcarrier are recovered and demodulated by determining the most likely signal constellation points transmitted by the base station 310. These soft decisions may be based on the channel estimates computed by the channel estimator 358. The soft decisions are then decoded and deinterleaved to recover the data and control signals originally transmitted by the base station 310 on the physical channel. The data and control signals are then provided to the controller / processor 359, which implements layer 3 and layer 2 functions.

[0048] The controller / processor 359 may be associated with a memory 360 that stores program code and data. The memory 360 may be referred to as a computer-readable medium. In the UL, the controller / processor 359 provides demultiplexing, packet reassembly, decryption, header decompression, and control signal processing between the transport channel and the logical channel to recover the IP packets from the EPC 160. The controller / processor 359 is also responsible for supporting error detection for HARQ operations using the ACK and / or NACK protocols.

[0049] Similar to the functions described in connection with DL transmissions performed by the base station 310, the controller / processor 359 provides: RRC layer functions associated with: system information (e.g., MIB, SIB) capture, RRC connection, and measurement reporting; PDCP layer functions associated with: header compression / decompression, and security (encryption, decryption, integrity protection, integrity verification); RLC layer functions associated with: transmission of upper layer PDUs, error correction via ARQ, concatenation, segmentation, and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and re-ordering of RLC data PDUs; and MAC layer functions associated with: mapping between logical channels and transport channels, multiplexing of MAC SDUs onto TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction via HARQ, priority handling, and logical channel prioritization.

[0050] The TX processor 368 may use channel estimates derived by the channel estimator 358 based on reference signals or feedback transmitted by the base station 310 to select appropriate decoding and modulation schemes and facilitate spatial processing. The spatial streams generated by the TX processor 368 may be provided to different antennas 352 via a separate transmitter 354TX. Each transmitter 354TX may modulate the RF carrier using the corresponding spatial stream for transmission.

[0051] At the base station 310, UL transmissions are processed in a manner similar to that described in connection with the receiver functions at the UE 350. Each receiver 318RX receives signals via its corresponding antenna 320. Each receiver 318RX recovers the information modulated onto the RF carrier and provides the information to the RX processor 370.

[0052] The controller / processor 375 may be associated with a memory 376 that stores program code and data. The memory 376 may be referred to as a computer-readable medium. In the UL, the controller / processor 375 provides demultiplexing, packet reassembly, decryption, header decompression, and control signal processing between the transport channel and the logical channel to recover IP packets from the UE 350. The IP packets from the controller / processor 375 may be provided to the EPC 160. The controller / processor 375 is also responsible for supporting error detection for HARQ operations using the ACK and / or NACK protocols.

[0053] At least one of the TX processor 368, the RX processor 356, and the controller / processor 359 may be configured to perform aspects related to Figure 1 the UL path switching component 140.

[0054] Figure 4 An example of a protocol architecture 400 that supports a split bearer configuration 402 in accordance with aspects of the present disclosure is shown. The protocol architecture 400 may include protocol stacks 405-a, 405-b, which may include a plurality of protocol entities that are common to both the user and control planes in the protocol stacks 405-a, 405-b. In some examples, the protocol architecture 400 may implement aspects of the wireless communication system 100, as described with reference to Figure 1 For example, the protocol architecture 400 may support dual connectivity using split bearers. Additionally, the protocol architecture 400 may support packet duplication, and more specifically, support PDCP duplication. For example, with reference to Figure 1 , the UE 104 may use a first protocol stack for packet transmission to one or more base stations associated with the MCG (MCG stack 405-b) and a second protocol stack for packet transmission to a base station associated with the SCG (SCG stack 405-b). For example, in aspects that may be used for E-UTRAN New Radio - Dual Connectivity (EN-DC), the MCG may utilize a first radio access technology (RAT) (e.g., LTE), and the SCG may utilize a second RAT (e.g., 5G NR). For example, the MCG may include a base station 102 configured for 4G LTE, and the SCG may include a base station 180 configured for 5G NR. Thus, the protocol architecture 400 may support configuration-based dual connectivity for the UE 104 to experience reduced power consumption, improved packet transmission reliability, increased spectral efficiency, higher data rates, and in some examples, experience low latency for wireless communication, as well as other benefits.

[0055] The protocol stack 405-a may include a Service Data Adaptation Protocol (SDAP) layer 415, a PDCP entity 420, a Radio Link Control (RLC) layer 425, a Medium Access Control (MAC) layer 430, and a Physical (PHY) layer 435. Each layer may be implemented by one or more entities. For example, the RLC layer 425 may include an RLC entity 425-a. The protocol stack 405-b may include a subset of protocol layers and entities as the MCG stack 405-a. For example, the protocol stack 405-b may also include an RLC entity 425-b at the RLC layer 425, a MAC entity 430-b at the MAC layer 430, and a PHY entity 435-b at the PHY layer 435. As will be further explained in detail below, the SCG stack 405-b may share the SDAP layer 415 and the PDCP entity 420 of the MCG stack 405-a. Multiple protocol entities may communicate with each other via one or more radio bearers, logical channels, and transport channels. For example, the SDAP layer 415 and the PDCP entity 420 may communicate with the RLC layer 425 via one or more radio bearers, the RLC layer 425 may communicate with the MAC layer 430 via one or more logical channels, and the MAC layer 430 may communicate with the PHY layer 435 via one or more transport channels. The radio bearers may include signaling radio bearers (SRBs), such as SRB0, SRB1, SRB2, SRB3, etc. Examples of logical channels include Broadcast Control Channel (BCCH), Paging Control Channel (PCCH), Common Control Channel (CCCHH), Dedicated Control Channel (DCCH), Dedicated Traffic Channel (DTCH), Multicast Traffic Channel (MCH), or Multicast Control Channel (MCCH). Examples of transport channels include Uplink Shared Channel (UL-SCH), Downlink Shared Channel (DL-SCH), Paging Channel (PCH), Broadcast Channel (BCH), Random Access Channel (RACH).

[0056] The SDAP layer 415 may support and perform various functions, such as mapping between Quality of Service (QoS) flows and data radio bearers, and assigning QoS flow identifiers to uplink packets. In some examples, the SDAP layer 415 may receive an uplink packet 440 and may assign the uplink packet 440 to a QoS flow and a radio bearer set to ensure that the uplink packet 440 receives proper forwarding processing when traversing the protocol stacks 405-a, 405-b. For example, the SDAP layer 415 may forward the uplink packet 440 to the PDCP entity 420 according to the assigned QoS flow and radio bearer set. The uplink packet 440 may be a PDCP service data unit (SDU).

[0057] The PDCP entity 420 may support and perform various PDCP layer functions, such as the transmission of user data, header compression, sequence numbering, duplicate detection, packet duplication, etc. In some examples, the PDCP entity 420 may receive an uplink packet 440 (e.g., PDCP SDU), and may perform header compression after encryption. In some examples, the PDCP entity 420 may add a PDCP header carrying information for decrypting the uplink packet 440. The PDCP entity 420 may route different uplink packets 445, 450 to different RLC entities within the RLC layer 425. In an example split bearer configuration, the PDCP entity 420 may route the uplink packets 445, 450 only to the primary RLC entity (e.g., RLC entity 425-a), unless the level of the data meets the transmit buffer threshold (which may also be referred to as the uplink data split threshold or ul-DataSplitThreshold). If the level of the data meets the transmit buffer threshold, the PDCP entity 420 may route the uplink packet to the primary RLC entity or the secondary RLC entity (e.g., RLC entity 425-b). In an example of packet duplication, the PDCP entity 420 may perform packet duplication on the uplink packet 440 (e.g., PDCP PDU), also referred to as "PDCP duplication". Thus, the PDCP entity 420 may generate uplink packets 445, 450 that may be fully or partially equivalent (e.g., differences in radio bearer identifier, logical channel identifier). For example, the uplink packet 445 may be associated with a different radio bearer and logical channel than the uplink packet 450. In some examples, the PDCP entity 420 performs packet duplication on the uplink packet 440 based on an uplink packet duplication configuration, which may be an uplink PDCP duplication configuration. In some examples, the PDCP entity 420 may perform packet duplication to generate multiple copies of the uplink packet 440.

[0058] The RLC layer 425 may include a primary RLC entity 425-a associated with the MCG and a secondary RLC entity 425-b associated with the SCG. In one implementation, when the level of uplink traffic is below the transmit buffer threshold, the PDCP entity 420 may route the uplink packets only to the primary RLC entity 425-a, but when the level of uplink traffic is equal to or higher than the transmit buffer threshold, the PDCP entity 420 may route the uplink packets to the primary RLC entity 425-a or the secondary RLC entity 425-b. For example, the PDCP entity 420 may forward the uplink packet 445 to the RLC entity 425-a in the protocol stack 405-a, and forward the uplink packet 450 to the RLC entity 425-b in the protocol stack 405-b. Using two RLC entities can allow for a higher uplink data rate using dual connectivity. The base station 102 may configure the RLC entities 425-a, 425-b and the uplink buffer threshold. In some examples, each RLC layer 425 may have one or more logical channels associated with one or more serving cells or carriers via logical channel mapping criteria. Each RLC layer 425 may assemble the uplink packets 445, 450 (e.g., RLC SDUs) received from the corresponding PDCP entity 420 into further groups of one or more packets (e.g., RLC PDUs), and may pass the groups of packets to the corresponding MAC layer 430.

[0059] The MAC layer 430 may perform logical channel prioritization, and may assemble the groups of one or more packets (e.g., MAC SDUs) received from the RLC layer 425 into MAC PDUs (i.e., transport blocks (TBs)), which are passed to the lower layer (e.g., PHY layer 435) for transmission over the radio interface. In a split bearer configuration, the MAC layer 430 may include a first MAC entity 430-a and a second MAC entity 430-b corresponding to the first RLC entity 425-a and the second RLC entity 425-b, respectively. Similarly, the PHY layer 435 may include a first PHY entity 435-a and a second PHY entity 435-b corresponding to the first RLC entity 425-a and the second RLC entity 425-b, respectively. For example, the uplink packets 445, 450 may be sent in parallel across multiple carriers (e.g., via carrier aggregation) or on multiple base stations 102, and each base station 102 may or may not use carrier aggregation. In some examples, additionally or alternatively, the uplink packets 445, 450 may be sent in parallel across multiple carriers on a directional beam. Thus, the protocol architecture 400 may use split bearers to support PDCP duplication with dual connectivity.

[0060] Figure 5FIG. 500 is an example transmission using protocol architecture 400 and split bearer configuration 402. As discussed with respect to Figure 4 the PDCP entity 420 may route PDCP PDUs to the primary RLC entity 425-a and / or the secondary RLC entity 425-b. Each RLC entity may include a respective transmit buffer 520-a storing RLC PDUs for transmission. The total transmit buffer level may be the sum of the individual transmit buffer levels. At a first time 502, the primary RLC entity 425-a may include 4 RLC PDUs with sequence numbers (SNs) k–k+3. In this example, the total transmit buffer level (e.g., 4 RLC PDUs) may be less than the transmit buffer threshold 510. Thus, the PDCP entity 420 may route all uplink packets to the primary RLC entity 425-a.

[0061] In one aspect, the primary RLC entity 425-a may encounter problems such as detachment of a second SIM. Accordingly, the MAC entity 430-a and the PHY entity 435-a associated with the RLC entity 425-a may be temporarily unavailable, and the RLC PDUs in the buffer 520-a may not be transmitted. When the number of RLC PDUs reaches the transmit buffer threshold 510, the PDCP entity 420 may route some RLC PDUs to the secondary RLC entity 425-b while also routing some RLC PDUs to the primary RLC entity 425-a. Thus, at a second time 504, when the data volume is greater than or equal to the transmit buffer threshold 510, the buffer 520-a may include 4 unsent RLC PDUs with SNs k–k+3 and new PDUs with SNs k+6 and k+7. The connection for the secondary RLC entity 425-b may not encounter the same problems, and the MAC entity 430-b and the PHY entity 435-b may be able to transmit RLC PDUs in the buffer 520-b. Accordingly, the receive buffer 530 at the receiving device (e.g., base station 180) may receive RLC PDUs with SNs k+4, k+5, k+8, and k+9. As shown, these PDUs may be received out of order. Thus, the receiving device may report the missing RLC PDUs and wait for RLC retransmission before performing RLC reordering.

[0062] Figure 6FIG. 600 is an example transmission using protocol architecture 400 and split bearer configuration 402. In this example, the transmit buffer threshold may be relatively low such that the PDCP entity 420 routes packets via both the primary RLC entity 425-a and the secondary RLC entity 425-b. For example, the PDCP entity 420 may alternate RLC entities every two PDUs. In one aspect, the (shown) primary RLC entity 425-a or secondary RLC entity 425-b may encounter problems such as the detachment of the second SIM. Another RLC entity (e.g., RLC entity 425-b) may continue to transmit RLC PDUs. Thus, the receive buffer 530 at the receiving device (e.g., base station 180) may receive RLC PDUs with SNs k+2, k+3, k+6, k+7, k+10, and k+11. As shown, these PDUs may be received out of order. Thus, the receiving device may report the missing RLC PDUs and wait for RLC retransmission before performing RLC reordering.

[0063] Figure 7 FIG. 700 is an example transmission using protocol architecture 400 and split bearer configuration 402 with PDCP duplication. That is, the PDCP entity 420 may duplicate uplink packets and route a copy of each packet via both the primary RLC entity 425-a and the secondary RLC entity 425-b. In one aspect, the (shown) primary RLC entity 425-a or secondary RLC entity 425-b may encounter problems such as the detachment of the second SIM at the first time 702. Another RLC entity (e.g., RLC entity 425-b) may continue to transmit RLC PDUs. Thus, the receive buffer 530 at the receiving device (e.g., base station 180) may receive RLC PDUs with SNs k–SN k+7 in order. Thus, PDCP duplication helps reduce latency in the event of a temporary event such as detachment. However, once the primary RLC entity 425-a returns from detachment at time 704, the buffer 520-a may still include expired PDUs that have been sent via the secondary RLC entity and received at the receive buffer 530. Thus, PDCP duplication may be less effective after the recovery of the primary RLC entity 425-a until the primary RLC entity 425-a clears the buffer 520-a. That is, although the PDCP entity 420 duplicates uplink packets, due to the longer queue at the primary RLC entity 425-a, the receive buffer 530 may typically receive PDUs from the secondary RLC entity 425-b first.

[0064] Figure 8800 is a diagram illustrating an example of a split bearer architecture with UL path switching. During a first time period 802, the UE 104 may operate with the protocol architecture 400 and the split bearer configuration. That is, when the UE 104 may transmit via both the MCG stack 405-a and the SCG stack 405-b, the UE 104 may transmit via the MCG stack 405-a unless the uplink buffer level meets the transmit buffer threshold. The PDCP entity 420 may receive an uplink switch start indication 810. For example, the uplink switch start indication 810 may be an indication from a lower layer (e.g., an RLC entity 425-a, a MAC entity 430-a, or a PHY entity 435-a) that radio frequency resources are to be used for tuning away. Therefore, the RLC entity 425-a may be temporarily unable to send packets. Other events may also generate a switch start indication 810. For example, a lower layer may generate a switch start indication 810 based on an indication of poor channel conditions. For example, the bad channel condition may include a number of retransmissions exceeding a threshold or a block error rate (BLER) exceeding a threshold. As another example, the handover start indication 810 may be generated by a higher layer (e.g., SDAP layer 415) in response to an indication of a low-latency service (e.g., configuration of a QoS flow with a low-latency requirement).

[0065] In one aspect, in response to a handover start indication 810, during a second time period 804, the PDCP entity 420 may enter a handover mode 840, where the PDCP entity 420 may route uplink packets to the RLC entity 425-b instead of the RLC entity 425-a. The PDCP entity 420 may route uplink packets to the RLC entity 425-b regardless of the uplink buffer level. The SCG stack 405-b may require an uplink grant to transmit to the SCG. Due to the split bearer configuration, the network may provide a grant only for the SCG stack 405-b when the uplink buffer level meets the transmit buffer threshold. To obtain a grant for transmitting uplink packets from the SCG stack 405-b, the SCG stack 405-b (e.g., the MAC entity 430-b) may send a buffer status report based on the current transmit buffer level plus the transmit buffer threshold. Thus, the UE 104 may receive a grant for transmission to the SCG to send the RLC PDUs routed by the PDCP entity 420. During, for example, a deactivation period 820, the lower layers of the MCG stack 405-a may be unavailable. However, the PDCP entity 420 may route all uplink packets to the RLC entity 425-b for transmission to the SCG. Thus, uplink communication may continue without interruption. In one aspect, when in the handover mode, the PDCP entity 420 may not route packets to the primary RLC entity 425-a. Thus, when the lower layers are unavailable, the buffer 520-a may not be filled with RLC PDUs.

[0066] The PDCP entity 420 may receive a handover stop indication 830, which indicates that the condition triggering the handover start indication 810 has been completed. For example, the MAC entity 430-a may provide the handover stop indication 830 after the end of the deactivation time period 820. In one aspect, the handover stop indication 830 may occur after a protection time period 832. The protection time period 832 may be configured based on the scheduling request of the UE 104. For example, the protection time period 832 may provide sufficient time for the SCG stack 405-b to send a scheduling request and a buffer status report to obtain a grant for transmitting any RLC PDUs in the transmit buffer 530-b.

[0067] After the handover stop indication 830, during a time period 806, the protocol architecture 400 may return to the normal operation mode, in which the PDCP entity 420 routes uplink packets to the primary RLC entity 425-a unless the current transmit buffer level meets the transmit buffer threshold.

[0068] Figure 9Message diagram 900 shows messages for split bearer communication with uplink path switching. UE 104 may be configured with a split bearer configuration, where base station 102 is the primary cell of the MCG and base station 180 is the primary cell of the SCG. In one aspect, base station 102 may be used for a first radio access technology (RAT), and base station 180 may be used for a second RAT. For example, base station 102 may be an LTE base station, and base station 180 may be a 5G NR base station. Base station 102 and base station 180 may communicate via a backhaul link 134. For example, base station 180 may forward received uplink packets to base station 102. As discussed above with respect to Figure 4 UE 104 may include an MCG stack 405-a and an SCG stack 405-b for communicating according to the respective RATs.

[0069] In normal mode with a split bearer configuration, UE 104 may send RLC PDUs 905 to base station 102 via the MCG stack 405-a. If the transmit buffer level meets the transmit buffer threshold, UE 104 may optionally send RLC PDUs 910 to base station 180 via the SCG stack 405-b. At 915, base station 180 may forward PDU 910 to base station 102.

[0070] The UE 104 may detect a handover start indication 920. The handover start indication 920 may correspond to the handover start indication 810. The handover start indication 920 may be an indication to the PDCP entity 420 to enter a handover mode. In response to the handover start indication, in the handover mode, the PDCP entity 420 may route uplink packets (e.g., PDCP PDUs or RLC SDUs) to one or more RLC entities 425-b of the SCG stack 405-b. In the handover mode, the UE 104 may send a scheduling request (SR) 925 to the base station 180 via the SCG stack 405-b (e.g., the PHY entity 435-b). The UE 104 may send a buffer status report (BSR) 930 to the base station 180 via the SCG stack 405-b (e.g., the MAC entity 430-b). The BSR 930 may indicate a transmit buffer level based on a current transmit buffer level plus a transmit buffer threshold. Thus, based on the BSR 930, the base station 180 and / or the base station 102 may determine that the UE 104 has uplink traffic for the SCG. The base station 180 may send a grant 935 indicating resources for the UE 104 to use for transmission of the SCG. For example, the grant 935 may be downlink control information (DCI) or a configured grant (CG). The UE 104 may send an RLC PDU 940 to the base station 180 via the SCG stack 405-b based on the grant 935. At 945, the base station 180 may forward the received RLC PDU 940 to the base station 102, which may include an RLC entity for the network.

[0071] The UE 104 may detect a handover stop indication 950. The handover stop indication 950 may correspond to the handover stop indication 830. For example, the handover stop indication 950 may be generated after an event such as a tune-away time period 820 ends. The handover stop indication 950 may be generated after a protection time period 832 to allow the SCG stack 405-b to obtain permission and send RLC PDUs in a transmit buffer before returning to normal mode. In response to the handover stop indication 950, the UE 104 may return to normal mode, where the UE 104 may send RLC PDUs 955 via the MCG stack 405-a, and optionally send RLC PDUs 960 via the SCG stack 405-b when a transmit buffer threshold is met.

[0072] Figure 10It is a flowchart of a method 1000 for wireless communication. The method 1000 can be performed by a UE or a component of the UE (e.g., UE 104; device 1102 / 1102'; processing system 1214, which can include a memory 360 and which can be the entire UE 350 or a component of the UE 350, such as a TX processor 368, an RX processor 356, and / or a controller / processor 359). The method can provide continuous transmission when the transmission path is temporarily unavailable and improve the recovery time and / or latency when the transmission path becomes available again.

[0073] At block 1010, the method 1000 can include: sending an uplink transmission from the UE using an uplink split bearer configuration from a PDCP entity on one or both of a first RLC entity associated with the MCG and a second RLC entity associated with the SCG, the configuration including a transmit buffer threshold. For example, block 1010 can be performed by a PDCP component 1112. The PDCP component 1112 can receive uplink data from an application 1120. For example, the PDCP component 1112 can receive uplink data via the SDAP layer. The PDCP component 1112 can generate an uplink packet such as a PDCP PDU and route the PDCP PDU to one or more RLC entities based on the uplink split bearer configuration and / or PDCP duplication. For example, with the split bearer configuration, the PDCP component 1112 can route the PDCP PDU to the first RLC entity associated with the MCG and optionally route the PDCP PDU to the second RLC entity associated with the SCG (e.g., when the current buffer status level meets the transmit buffer threshold). If PDCP duplication is active, the PDCP component 1112 can route the PDCP PDU to both the first RLC entity and the second RLC entity.

[0074] At block 1020, the method 1000 can include: receiving an uplink handover start indication at the PDCP entity. Block 1020 can be performed by a handover component 1114. For example, the handover component 1114 can receive a handover start indication from another component that detects a condition triggering an uplink path handover. For example, the handover can be based on a configuration for the MAC layer or the PHY layer. Thus, at sub-block 1022, the handover component 1114 can receive a handover start indication from the MAC layer or the PHY layer. As another example, at sub-block 1024, the handover component 1114 can receive an indication of low latency traffic from a higher layer (such as an application 1120 indicating low latency traffic (e.g., by using a specific QoS flow)). As another example, at sub-block 1026, the handover component 1114 can receive an indication of a poor channel condition generated by the RLC layer or the MAC layer.

[0075] At block 1030, method 1000 may include activating a second RLC entity in response to receiving an uplink handover start indication. Block 1030 may be performed by an RLC control component 1116. For example, the RLC control component 1116 may designate a second RLC entity (e.g., RLC entity 425-b) as an active RLC entity. At subblock 1032, block 1030 may include forwarding packets to one or more RLC entities for the SCG. For example, PDCP duplication may allow multiple RLC entities for a cell group. The RLC control component 1116 may activate each of the RLC entities for the SCG and forward packets to each of the active RLC entities for the SCG.

[0076] At block 1040, method 1000 may include sending a buffer status report based on a current transmit buffer level plus a transmit buffer threshold. For example, block 1040 may be performed by a buffer component 1118. The buffer component 1118 may store RLC PDUs for one or more RLC entities prior to transmission. The buffer component 1118 may determine a current buffer level (e.g., an amount of data in the RLC PDU). When in switching mode, the buffer component 1118 may add the buffer transmit threshold to the current buffer level when generating a buffer status report. Thus, the buffer status report may indicate a higher level of data to be sent than the data stored in the buffer component 1118 in order to trigger an uplink grant for the SCG. In one implementation, at subblock 1042, the buffer component 1118 may send a buffer status report from a medium access control entity corresponding to a second RLC entity. For example, the buffer component 1118 may send the BSR 930 via the MAC entity 430-b.

[0077] At block 1050, method 1000 may optionally include receiving an uplink handover stop indication at the PDCP entity. Block 1050 may be performed by handover component 1114. For example, the uplink handover stop indication may correspond to an event that triggers a handover start indication. Thus, handover component 1114 may receive a tune-away stop indication, an indication of an end of a low-latency service, or an indication of an end of a poor channel condition.

[0078] At block 1060, method 1000 may optionally include deactivating a second RLC entity in response to receiving an uplink handover stop indication after expiration of a protection period. Block 1060 may be performed by RLC control component 1116. For example, RLC control component 1116 may deactivate one or more RLC entities of SCG stack 405-b. As discussed above, protection period 832 may allow the second RLC entity time to request and receive permission to transmit remaining RLC PDUs stored in buffer component 1118.

[0079] Figure 11 Conceptual data flow diagram 1100 shows data flows between different units / components in example device 1102. The device may be a UE or a component of a UE. Device 1102 includes a receiving component 1104 that receives downlink signaling (such as an RRC message) from a base station (such as base station 102 or base station 180). Device 1102 includes a configuration component 1106 that receives an RRC message from receiving component 1104 and extracts various configurations. For example, configuration component 1106 may extract split bearer configurations for configuring PDCP component 1112 and SR configurations for PHY layer configurations for transmitting component 1110. Device 1102 includes a transmitting component 1110 that performs lower layer (e.g., MAC layer and PHY layer) processing for uplink transmissions. For example, transmitting component 1110 may transmit a PHY layer signal carrying a MAC transport block including RLC PDUs to one or both of base station 102 and base station 180.

[0080] Device 1102 includes a PDCP component 1112 that uses an uplink split bearer configuration to transmit uplink transmissions. That is, PDCP component 1112 may perform PDCP layer processing, which includes routing PDCP PDUs to one or both of a first RLC entity associated with MCG and a second RLC entity associated with SCG, e.g., as described in connection with block 1010. Device 1102 includes a handover component 1114 that receives a handover start indication, e.g., as described in connection with block 1020. Handover component 1114 may also receive a handover stop indication, e.g., as described in connection with block 1050. Device 1102 includes an RLC control component 1116 that activates a second RLC entity in response to receiving an uplink handover start indication, e.g., as described in connection with block 1030. RLC control component 1116 may also deactivate the second RLC entity in response to receiving a handover stop indication, e.g., as described in connection with block 1060. In one aspect, PDCP component 1112, handover component 1114, and RLC control component 1116 may be components of PDCP entity 420.

[0081] The apparatus 1102 includes a buffer component 1118 that transmits a buffer status report based on a current transmit buffer level plus a transmit buffer threshold, e.g., as described in connection with block 1040. In one aspect, the buffer component 1118 can be a component of an RLC entity (e.g., RLC entity 425-b). The buffer component 1118 can transmit the buffer status report via an associated MAC entity (e.g., MAC entity 430-b), which can be implemented by the transmit component 1110.

[0082] The apparatus can include additional components that perform each block in the algorithms in the Figure 10 flowcharts described above. As such, each block in the Figure 10 flowcharts described above can be performed by a component, and the apparatus can include one or more of those components. The components can be one or more hardware components specifically configured to perform the processes / algorithms, implemented by a processor configured to perform the processes / algorithms, stored within a computer-readable medium for implementation by a processor, or some combination thereof.

[0083] Figure 12 FIG. 1200 is a diagram illustrating an example of a hardware implementation of an apparatus 1102' employing a processing system 1214. The processing system 1214 can be implemented using a bus architecture, generally represented by bus 1224. Bus 1224 can include any number of interconnecting buses and bridges, depending on the specific application of the processing system 1214 and overall design constraints. Bus 1224 links together various circuits including one or more processors and / or hardware components (represented by processor 1204, components 1104, 1106, 1110, 1112, 1114, 1116, 1118, and computer-readable medium / memory 1206). Bus 1224 also links together various other circuits such as a timing source, peripherals, voltage regulators, and power management circuits, which are well known in the art and will not be described any further herein.

[0084] The processing system 1214 can be coupled to the transceiver 1210. The transceiver 1210 is coupled to one or more antennas 1220. The transceiver 1210 provides means for communicating with various other devices over a transmission medium. The transceiver 1210 receives signals from one or more antennas 1220, extracts information from the received signals, and provides the extracted information to the processing system 1214 (specifically, the receiving component 1104). Additionally, the transceiver 1210 receives information from the processing system 1214 (specifically, the transmitting component 1110) and generates signals to be applied to one or more antennas 1220 based on the received information. The processing system 1214 includes a processor 1204 coupled to a computer-readable medium / memory 1206. The processor 1204 is responsible for general processing, which includes the execution of software stored on the computer-readable medium / memory 1206. The software, when executed by the processor 1204, causes the processing system 1214 to perform the various functions described above for any particular device. The computer-readable medium / memory 1206 can also be used to store data manipulated by the processor 1204 when executing the software. The processing system 1214 also includes at least one of components 1104, 1106, 1110, 1112, 1114, 1116, 1118. The components can be software components running in the processor 1204, located / stored in the computer-readable medium / memory 1206, one or more hardware components coupled to the processor 1204, or some combination thereof. The processing system 1214 can be a component of the UE 350 and can include a memory 360 and / or at least one of the following: a TX processor 368, an RX processor 356, and a controller / processor 359. Alternatively, the processing system 1214 can be the entire UE (e.g., see Figure 3 the UE 350).

[0085] In one configuration, the apparatus 1102 / 1102' for wireless communication includes: means for transmitting an uplink transmission from a user equipment using an uplink split bearer configuration from the packet data convergence protocol (PDCP) layer on one or both of a first radio link control (RLC) entity associated with a master cell group (MCG) and a second RLC entity associated with a secondary cell group (SCG), the configuration including a transmit buffer threshold; means for receiving an uplink handover start indication at a PDCP entity; means for activating the second RLC entity in response to receiving the uplink handover start indication; and means for transmitting a buffer status report based on a current transmit buffer level plus the transmit buffer threshold.

[0086] The above unit may be one or more of the above components of apparatus 1102 and / or a processing system 1214 of apparatus 1102' configured to perform the functions recited by the above unit. As described above, the processing system 1214 may include a TX processor 368, an RX processor 356, and a controller / processor 359. Thus, in one configuration, the above unit may be the TX processor 368, the RX processor 356, and the controller / processor 359 configured to perform the functions recited by the above unit.

[0087] In view of the foregoing, uplink path switching provides continuous transmission from the UE in the event that the transmission path for the MCG becomes temporarily unavailable. Further, by switching the uplink transmission path to the SCG, the transmission path for the MCG can be restored more quickly without having to purge expired uplink data packets. Additionally, a handover stop indication can be used to restore the transmission path for the MCG and provide a guard period to purge uplink data packets from the transmission path for the SCG. In an implementation where the MCG is associated with LTE and the SCG is associated with 5G NR, uplink path switching can improve latency when an indication of low latency traffic triggers an uplink handover start indication.

[0088] It should be understood that the specific order or hierarchy of the blocks in the disclosed process / flowchart is an illustration of an example method. Based on design preferences, it should be understood that the specific order or hierarchy of the blocks in the process / flowchart can be rearranged. Additionally, some blocks may be combined or omitted. The appended method claims present the elements of the various blocks in a sample order, but are not meant to be limited to the specific order or hierarchy presented.

[0089] The foregoing description is provided to enable any person skilled in the art to make and use the various aspects described herein. Various modifications to these aspects will be apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but rather to the full scope consistent with the claims as expressed, where the mention of an element in the singular is not intended to mean "one and only one" but rather "one or more" unless explicitly stated otherwise. The term "exemplary" as used herein means "serving as an example, instance, or illustration". Any aspect described herein as "exemplary" need not be construed as preferred or superior to other aspects. Unless explicitly stated otherwise, the term "some" refers to one or more. Combinations such as "at least one of A, B, or C", "one or more of A, B, or C", "at least one of A, B, and C", "one or more of A, B, and C", and "any combination of A, B, C, or any combination thereof" include any combination of A, B, and / or C and may include multiples of A, multiples of B, or multiples of C. Specifically, combinations such as "at least one of A, B, or C", "one or more of A, B, or C", "at least one of A, B, and C", "one or more of A, B, and C", and "any combination of A, B, C, or any combination thereof" can be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any such combination can include one or more members or several members of A, B, or C. All structural and functional equivalents, known or later to be known to those of ordinary skill in the art, of the elements of the various aspects described throughout this disclosure are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public, whether or not such disclosure is explicitly recited in the claims. The terms "module", "mechanism", "element", "device", etc. are not intended to be substitutes for the term "unit". Thus, no claim element is to be construed as a functional unit unless the element is expressly recited using the phrase "unit for...".

Claims

1. A method of wireless communication, comprising: sending, on one or both of a first radio link control (RLC) entity associated with a primary cell group (MCG) and a second RLC entity associated with a secondary cell group (SCG), an uplink transmission from a user equipment (UE) using an uplink split bearer configuration from a packet data convergence protocol (PDCP) entity, the uplink split bearer configuration including a transmit buffer threshold; receiving, at the PDCP entity, an uplink handover start indication; activating the second RLC entity in response to receiving the uplink handover start indication; and A buffer status report is sent based on the sum of a current transmit buffer level and the transmit buffer threshold.

2. The method according to claim 1, further comprising: receiving, at the PDCP entity, an uplink switching stop indication; as well as The second RLC entity is deactivated in response to receiving the uplink switching stop indication after expiration of a guard period.

3. The method according to claim 2, wherein: The protection period is configured based on a scheduling request.

4. The method according to claim 1, wherein: Activating the second RLC entity includes forwarding packets to one or more RLC entities for the SCG.

5. The method according to claim 1, wherein: Sending the buffer status report includes sending the buffer status report from a medium access control entity corresponding to the second RLC entity.

6. The method according to claim 1, wherein: The MCG is associated with a first radio access technology (RAT) and the SCG is associated with a second RAT.

7. The method according to claim 1, wherein: Receiving the uplink handover start indication at the PDCP entity includes receiving a tune-away start indication.

8. The method according to claim 7, wherein: The tune away start indication is associated with a periodic tune away in a multiple subscriber identity module (SIM) device.

9. The method according to claim 1, wherein: Receiving the uplink switching start indication at the PDCP entity includes: receiving an indication of a low-latency service.

10. The method according to claim 1, wherein: Receiving the uplink handover start indication at the PDCP entity includes receiving an indication of a poor channel condition.

11. An apparatus for wireless communication, comprising: means for sending an uplink transmission from a user equipment using an uplink split bearer configuration from a packet data convergence protocol (PDCP) entity on one or both of a first radio link control (RLC) entity associated with a primary cell group (MCG) and a second RLC entity associated with a secondary cell group (SCG), the uplink split bearer configuration including a transmit buffer threshold; means for receiving, at the PDCP entity, an uplink handover start indication; means for activating the second RLC entity in response to receiving the uplink handover start indication; as well as Means for sending a buffer status report based on a sum of a current transmit buffer level and the transmit buffer threshold.

12. The device according to claim 11, wherein: The unit for receiving the uplink switching start indication is also configured to: receive an uplink switching stop indication at the PDCP entity; and wherein, the unit for activating the second RLC entity is configured to: deactivate the second RLC entity in response to receiving the uplink switching stop indication after expiration of a protection time period.

13. The device according to claim 12, wherein: The protection period is configured based on a scheduling request.

14. The device according to claim 11, wherein: The means for activating the second RLC entity is configured to forward packets to one or more RLC entities for the SCG.

15. The device according to claim 11, wherein The means for sending the buffer status report is configured to send the buffer status report from a medium access control entity corresponding to the second RLC entity.

16. The device according to claim 11, wherein The MCG is associated with a first radio access technology (RAT) and the SCG is associated with a second RAT.

17. The device according to claim 11, wherein: The means for receiving the uplink handover start indication at the PDCP entity is configured to receive a tune-away start indication.

18. The device according to claim 17, wherein: The tune away start indication is associated with a periodic tune away in a multiple subscriber identity module (SIM) device.

19. The device according to claim 11, wherein: The means for receiving the uplink switching start indication at the PDCP entity is configured to receive an indication of a low-latency service.

20. The device according to claim 11, wherein The means for receiving the uplink handover start indication at the PDCP entity is configured to receive an indication of a poor channel condition.

21. An apparatus for wireless communication, comprising: Memory; as well as at least one processor coupled to the memory and configured to: sending an uplink transmission from a user equipment using an uplink split bearer configuration from a packet data convergence protocol (PDCP) entity on one or both of a first radio link control (RLC) entity associated with a primary cell group (MCG) and a second RLC entity associated with a secondary cell group (SCG), the uplink split bearer configuration including a transmit buffer threshold; receiving, at the PDCP entity, an uplink handover start indication; activating the second RLC entity in response to receiving the uplink handover start indication; and A buffer status report is sent based on the sum of a current transmit buffer level and the transmit buffer threshold.

22. The device according to claim 21, wherein The at least one processor is configured to: receiving an uplink switching stop indication at the PDCP entity; and The second RLC entity is deactivated in response to receiving the uplink switching stop indication after expiration of a guard period.

23. The device according to claim 22, wherein: The protection period is configured based on a scheduling request.

24. The device according to claim 21, wherein The at least one processor is configured to forward packets to one or more RLC entities for the SCG when the second RLC entity is active.

25. The device according to claim 21, wherein The at least one processor is configured to send the buffer status report from a medium access control entity corresponding to the second RLC entity.

26. The device according to claim 21, wherein The MCG is associated with a first radio access technology (RAT) and the SCG is associated with a second RAT.

27. The device according to claim 21, wherein The at least one processor is configured to receive a tune away start indication as the uplink handover start indication.

28. The device according to claim 27, wherein The tune away start indication is associated with a periodic tune away in a multiple subscriber identity module (SIM) device.

29. The device according to claim 21, wherein The at least one processor is configured to receive an indication of low latency traffic or an indication of poor channel conditions as the uplink switching start indication.

30. A non-transitory computer readable medium storing computer executable code, which, when executed by a processor, causes the processor to: sending, on one or both of a first radio link control (RLC) entity associated with a primary cell group (MCG) and a second RLC entity associated with a secondary cell group (SCG), an uplink transmission from a user equipment using an uplink split bearer configuration from a packet data convergence protocol (PDCP) entity, the uplink split bearer configuration including a transmit buffer threshold; receiving, at the PDCP entity, an uplink handover start indication; activating the second RLC entity in response to receiving the uplink handover start indication; and A buffer status report is sent based on the sum of the current send buffer level and the send buffer threshold.

Images