WO2019006945A1

WO2019006945A1 - System and method for latency reduction with delay-sensitive traffic

Info

Publication number: WO2019006945A1
Application number: PCT/CN2017/109727
Authority: WO
Inventors: Haiqin LIU; Peng Wu; Gang Xiao; Jiming Guo; Arnaud Meylan; Rudhir Upretee; Shailesh Maheshwari; Saket BATHWAL; Xing Chen; Xiaojian LONG; Bao Vinh Nguyen; Ashwin Raman
Original assignee: Qualcomm Incorporated
Priority date: 2017-07-03
Filing date: 2017-11-07
Publication date: 2019-01-10
Also published as: WO2019006582A1

Abstract

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. In aspects, the apparatus may be a user equipment (UE). However, the apparatus may be implemented as another wireless communications device, such as a base station (e.g., evolved Node B). The apparatus may determine that the apparatus is to operate in a low-latency mode. The apparatus may configure at least one layer of the apparatus to operate in the low-latency mode based on the determination that the apparatus is to operate in the low-latency mode. The apparatus may communicate with a network through the configured at least one layer.

Description

SYSTEM AND METHOD FOR LATENCY REDUCTION WITH DELAY-SENSITIVE TRAFFIC

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Patent Application No. PCT/CN2017/091438, entitled “SYSTEM AND METHOD FOR LATENCY REDUCTION WITH DELAY-SENSITIVE TRAFFIC” filed on July 3, 2017, which is expressly incorporated by reference herein in its entirety.

BACKGROUND Field

The present disclosure relates generally to communication systems, and more particularly, to a user equipment configured to reduce latency associated with delay-sensitive traffic.

Background

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems 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.

These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is 5G New Radio (NR) . 5G NR is part of a continuous mobile broadband evolution promulgated by Third Generation Partnership Project (3GPP) to meet new requirements associated with latency, reliability, security, scalability (e.g., with Internet of Things (IoT) ) , and other requirements. Some aspects of 5G NR may be based on the 4G Long Term Evolution (LTE) standard. There exists a need for further improvements in 5G NR technology. These improvements may also be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

SUMMARY

The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor 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 presented later.

In some aspects, various real-time applications may be delay-sensitive, requiring a relatively short delay with a relatively minimal delay variation. Examples of real-time applications include multimedia applications, voice-over-internet protocol (VoIP) , video-conferencing applications, virtual reality applications and online games. Real-time requirements may present design issues at layers below the application layer, such as the modem layer. In particular, a latency issue may appreciably affect the user experience, such as when an online mobile game is repeatedly paused or lags due to issues originating at lower layers of a radio protocol stack (e.g., . due to radio impairments) .

In order to satisfy delay-sensitivity requirements, quality of service (QoS) differentiation may be implemented at the network. For different QoSs, separate streams may be used to transport data of different services. To support different QoSs, streams of different characteristics may be mapped to different bearers. A bearer may be a unit of QoS control, and one bearer may be used to fulfill one set of QoS requirements.

In Long Term Evolution (LTE) and/or other wireless communication standards, a parameter called the QoS Class Identifier (QCI) may be used. The QCI defines a unique expected treatment of a bearer and is intended to provide similar handling of bearers of the same QCI, e.g., even if network nodes are developed by different manufacturers. Based on a received QCI value, each network node knows how a given bearer is to be treated. QCI values may be specified within a 3GPP standard so that each vendor knows expected characteristics for a bearer with a given QCI value. The characteristics may include priority level, delay budget, packet loss rate, and so on.

However, QoS may be handled at a network side, for example, as opposed to a user equipment (UE) side. In some instances, a network side may not follow the expected characteristics for real-time applications. Moreover, a network side may provide a “best effort” service (e.g., the network side may not provide any guarantees that a UE will be provided a certain QoS) as it is not able to, or has no incentive to provide a QoS service for such applications. For example, while using a best effort service, when a network is congested, a packet delay budget may be unsatisfied. Even with QCI defined in a 3GPP standard, a UE-side application may lack a reliable mechanism to cause a network side to set up a transport layer with characteristics required for communication of delay-sensitive traffic (e.g., user datagram protocol (UDP) ) . Rather, a network side may set up a transport layer for delay-sensitive traffic where reliability is prioritized over low latency (e.g., transport control protocol (TCP) ) .

In view of the foregoing, a UE may benefit from one or more mechanisms implemented at the UE side to reduce latency. For example, the UE may perform various operations to reduce latency associated with UDP traffic, as UDP traffic is frequently associated with real-time applications. One or more layers of the UE may perform these various operations, either individually or in coordination. For example, with the help of the application layer, the modem layer may determine that the UE is configured to execute a real-time application and may switch to a mode associated with low latency. In such a mode, a UE may cause one bearer (e.g., a default bearer) to attempt to behave like a dedicated bearer that would provide a certain QoS even when the UE has not been provided such a dedicated bearer. Thus, the UE may cause low latency to be prioritized over reliability.

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. In aspects, the apparatus may be a UE. However, the apparatus may be implemented as another wireless communications device, such as a base station (e.g., evolved Node B) . The apparatus may determine that the apparatus is to operate in a low-latency mode. The apparatus may configure at least one layer of the apparatus to operate in the low-latency mode based on the determination that the apparatus is to operate in the low-latency mode. The apparatus may communicate with a network through the configured at least one layer.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a wireless communications system and an access network.

FIGs. 2A, 2B, 2C, and 2D are diagrams illustrating examples of a DL frame structure, DL channels within the DL frame structure, an UL frame structure, and UL channels within the UL frame structure, respectively.

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

FIG. 4A is a diagram of a wireless communications system.

FIG. 4B is a call flow diagram of a method of wireless communication.

FIG. 5 is a flowchart of a method of wireless communication.

FIG. 6 is a flowchart of a method of wireless communication.

FIG. 7 is a flowchart of a method of wireless communication.

FIG. 8 is a flowchart of a method of wireless communication.

FIG. 9 is a flowchart of a method of wireless communication.

FIG. 10 is a flowchart of a method ofwireless communication.

FIG. 11 is a flowchart of a method of wireless communication.

FIG. 12 is a flowchart of a method of wireless communication.

FIG. 13 is a flowchart of a method of wireless communication.

FIG. 14 is a flowchart of a method of wireless communication.

FIG. 15 is a flowchart of a method of wireless communication.

FIG. 16 is a flowchart of a method of wireless communication.

FIG. 17 is a flowchart of a method of wireless communication.

FIG. 18 is a flowchart of a method of wireless communication.

FIG. 19 is a flowchart of a method of wireless communication.

FIG. 20 is a flowchart of a method of wireless communication.

FIG. 21 is a flowchart of a method of wireless communication.

FIG. 22 is a conceptual data flow diagram illustrating the data flow between different means/components in an exemplary apparatus.

FIG. 23 is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system.

DETAILED DESCRIPTION

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 practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced 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.

Several aspects of telecommunication systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc. (collectively referred to as “elements” ) . 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.

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 microprocessors, microcontrollers, graphics processing units (GPUs) , central processing units (CPUs) , application processors, digital signal processors (DSPs) , reduced instruction set computing (RISC) processors, systems on a chip (SoC) , baseband processors, field programmable gate arrays (FPGAs) , programmable logic devices (PLDs) , state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. One or more processors in the processing system may execute software. Software shall 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, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

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

FIG. 1 is a diagram illustrating an example of a wireless communications system and an access network 100. The wireless communications system (also referred to as a wireless wide area network (WWAN) ) includes base stations 102, UEs 104, and an Evolved Packet Core (EPC) 160. The base stations 102 may include macro cells (high power cellular base station) and/or small cells (low power cellular base station) . The macro cells include base stations. The small cells include femtocells, picocells, and microcells.

The base stations 102 (collectively referred to as Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN) ) interface with the EPC 160 through backhaul links 132 (e.g., S1 interface) . In addition to other functions, the base stations 102 may perform one or more of the following functions: transfer of user data, radio channel ciphering and deciphering, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity) , inter-cell interference coordination, connection setup and release, load balancing, distribution for non-access stratum (NAS) messages, NAS node selection, synchronization, radio access network (RAN) sharing, multimedia broadcast multicast service (MBMS) , subscriber and equipment trace, RAN information management (RIM) , paging, positioning, and delivery of warning messages. The base stations 102 may communicate directly or indirectly (e.g., through the EPC 160) with each other over backhaul links 134 (e.g., X2 interface) . The backhaul links 134 may be wired or wireless.

The base stations 102 may wirelessly communicate with the UEs 104. Each of the base stations 102 may provide communication coverage for a respective geographic coverage area 110. There may be overlapping geographic coverage areas 110. For example, the small cell 102′may have a coverage area 110′that overlaps the coverage area 110 of one or more macro base stations 102. A network that includes both small cell and macro cells may be known as a heterogeneous network. A heterogeneous network may also include Home Evolved Node Bs (eNBs) (HeNBs) , which may provide service to a restricted group known as a closed subscriber group (CSG) . The communication links 120 between the base stations 102 and the UEs 104 may include uplink (UL) (also referred to as reverse link) transmissions from a UE 104 to a base station 102 and/or downlink (DL) (also referred to as forward link) transmissions from a base station 102 to a UE 104. The communication links 120 may use multiple-input and multiple-output (MIMO) antenna technology, including spatial multiplexing, beamforming, and/or transmit diversity. The communication links may be through one or more carriers. The base stations 102 /UEs 104 may use spectrum up to Y MHz (e.g., 5, 10, 15, 20, 100 MHz) bandwidth per carrier allocated in a carrier aggregation of up to a total of Yx MHz (x component carriers) used for transmission in each direction. The carriers may or may not be adjacent to each other. Allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or less carriers may be allocated for DL than for UL) . The component carriers may include a primary component carrier and one or more secondary component carriers. A primary component carrier may be referred to as a primary cell (PCell) and a secondary component carrier may be referred to as a secondary cell (SCell) .

Certain UEs 104 may communicate with each other using device-to-device (D2D) communication link 192. The D2D communication link 192 may use the DL/UL WWAN spectrum. The D2D communication link 192 may use one or more sidelink channels, such as a physical sidelink broadcast channel (PSBCH) , a physical sidelink discovery channel (PSDCH) , a physical sidelink shared channel (PSSCH) , and a physical sidelink control channel (PSCCH) . D2D communication may be through a variety of wireless D2D communications systems, such as for example, FlashLinQ, WiMedia, Bluetooth, ZigBee, Wi-Fi based on the IEEE 802.11 standard, Long Term Evolution (LTE) , or fifth generation (5G) new radio (NR) .

The wireless communications system may further include a Wi-Fi access point (AP) 150 in communication with Wi-Fi stations (STAs) 152 via communication links 154 in a 5 GHz unlicensed frequency spectrum. When communicating in an unlicensed frequency spectrum, the STAs 152 /AP 150 may perform a clear channel assessment (CCA) prior to communicating in order to determine whether the channel is available.

The small cell 102′may operate in a licensed and/or an unlicensed frequency spectrum. When operating in an unlicensed frequency spectrum, the small cell 102′may employ NR and use the same 5 GHz unlicensed frequency spectrum as used by the Wi-Fi AP 150. The small cell 102′, employing NR in an unlicensed frequency spectrum, may boost coverage to and/or increase capacity of the access network.

The gNodeB (gNB) 180 may operate in millimeter wave (mmW) frequencies and/or near mmW frequencies in communication with the UE 104. When the gNB 180 operates in mmW or near mmW frequencies, the gNB 180 may be referred to as an mmW base station. Extremely high frequency (EHF) is part of the RF in the electromagnetic spectrum. EHF has a range of 30 GHz to 300 GHz and a wavelength between 1 millimeter and 10 millimeters. Radio waves in the band may be referred to as a millimeter wave. Near mmW may extend down to a frequency of 3 GHz with a wavelength of 100 millimeters. The super high frequency (SHF) band extends between 3 GHz and 30 GHz, also referred to as centimeter wave. Communications using the mmW /near mmW radio frequency band has extremely high path loss and a short range. The mmW base station 180 may utilize beamforming 184 with the UE 104 to compensate for the extremely high path loss and short range.

The EPC 160 may include a Mobility Management Entity (MME) 162, other MMEs 164, a Serving Gateway 166, a Multimedia Broadcast Multicast Service (MBMS) Gateway 168, a Broadcast Multicast Service Center (BM-SC) 170, and a Packet Data Network (PDN) Gateway 172. The MME 162 may be in communication with a Home Subscriber Server (HSS) 174. The MME 162 is the control node that processes the signaling between the UEs 104 and the EPC 160. Generally, the MME 162 provides bearer and connection management. All user Internet protocol (IP) packets are transferred through the Serving Gateway 166, which itself is connected to the PDN Gateway 172. The PDN Gateway 172 provides UE IP address allocation as well as other functions. The PDN Gateway 172 and the BM-SC 170 are connected to the IP Services 176. The IP Services 176 may include the Internet, an intranet, an IP Multimedia Subsystem (IMS) , a PS Streaming Service, and/or other IP services. The BM-SC 170 may provide functions for MBMS user service provisioning and delivery. The BM-SC 170 may serve as an entry point for content provider MBMS transmission, 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. The MBMS Gateway 168 may be used to distribute MBMS traffic to the base stations 102 belonging to a Multicast Broadcast Single Frequency Network (MBSFN) area broadcasting a particular service, and may be responsible for session management (start/stop) and for collecting eMBMS related charging information.

The base station may also be referred to as a gNB, Node B, evolved Node B (eNB) , an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS) , an extended service set (ESS) , or some other suitable terminology. The base station 102 provides an access point to the EPC 160 for a UE 104. Examples of UEs 104 include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA) , a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player) , a camera, a game console, a tablet, a smart device, a wearable device, a vehicle, an electric meter, a gas pump, a toaster, or any other similar functioning device. Some of the UEs 104 may be referred to as IoT devices (e.g., parking meter, gas pump, toaster, vehicles, etc. ) . The UE 104 may also be referred to as a station, a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology.

Referring again to FIG. 1, in certain aspects, the UE 104 may determine that the UE 104 is to operate in a low-latency mode. The UE 104 may configure at least one layer of the UE 104 to operate in the low-latency mode based on the determination that the UE 104 is to operate in the low-latency mode. The UE 104 may communicate 198 with a network (e.g., the base station 102) through the at least one layer of the UE 104 that is configured to operate in the low-latency mode.

FIG. 2A is a diagram 200 illustrating an example of a DL frame structure. FIG. 2B is a diagram 230 illustrating an example of channels within the DL frame structure. FIG. 2C is a diagram 250 illustrating an example of an UL frame structure. FIG. 2D is a diagram 280 illustrating an example of channels within the UL frame structure. Other wireless communication technologies may have a different frame structure and/or different channels. A frame (10 ms) may be divided into 10 equally sized subframes. Each subframe may include two consecutive time slots. A resource grid may be used to represent the two time slots, each time slot including one or more time concurrent resource blocks (RBs) (also referred to as physical RBs (PRBs) ) . The resource grid is divided into multiple resource elements (REs) . For a normal cyclic prefix, an RB may contain 12 consecutive subcarriers in the frequency domain and 7 consecutive symbols (for DL, OFDM symbols; for UL, SC-FDMA symbols) in the time domain, for a total of 84 REs. For an extended cyclic prefix, an RB may contain 12 consecutive subcarriers in the frequency domain and 6 consecutive symbols in the time domain, for a total of 72 REs. The number of bits carried by each RE depends on the modulation scheme.

As illustrated in FIG. 2A, some of the REs carry DL reference (pilot) signals (DL-RS) for channel estimation at the UE. The DL-RS may include cell-specific reference signals (CRS) (also sometimes called common RS) , UE-specific reference signals (UE-RS) , and channel state information reference signals (CSI-RS) . FIG. 2A illustrates CRS for

antenna ports

0, 1, 2, and 3 (indicated as R₀, R₁, R₂, and R₃, respectively) , UE-RS for antenna port 5 (indicated as R₅) , and CSI-RS for antenna port 15 (indicated as R) .

FIG. 2B illustrates an example of various channels within a DL subframe of a frame. The physical control format indicator channel (PCFICH) is within symbol 0 of slot 0, and carries a control format indicator (CFI) that indicates whether the physical downlink control channel (PDCCH) occupies 1, 2, or 3 symbols (FIG. 2B illustrates a PDCCH that occupies 3 symbols) . The PDCCH carries downlink control information (DCI) within one or more control channel elements (CCEs) , each CCE including nine RE groups (REGs) , each REG including four consecutive REs in an OFDM symbol. A UE may be configured with a UE-specific enhanced PDCCH (ePDCCH) that also carries DCI. The ePDCCH may have 2, 4, or 8 RB pairs (FIG. 2B shows two RB pairs, each subset including one RB pair) . The physical hybrid automatic repeat request (ARQ) (HARQ) indicator channel (PHICH) is also within symbol 0 of slot 0 and carries the HARQ indicator (HI) that indicates HARQ acknowledgement (ACK) /negative ACK (NACK) feedback based on the physical uplink shared channel (PUSCH) . The primary synchronization channel (PSCH) may be within symbol 6 of slot 0 within

subframes

0 and 5 of a frame. The PSCH carries a primary synchronization signal (PSS) that is used by a UE 104 to determine subframe/symbol timing and a physical layer identity. The secondary synchronization channel (SSCH) may be within symbol 5 of slot 0 within

subframes

0 and 5 of a frame. The SSCH carries a secondary synchronization signal (SSS) that is used by a UE to determine a physical layer cell identity group number and radio frame timing. Based on the physical layer identity and the physical layer cell identity group number, the UE can determine a physical cell identifier (PCI) . Based on the PCI, the UE can determine the locations of the aforementioned DL-RS. The physical broadcast channel (PBCH) , which carries a master information block (MIB) , may be logically grouped with the PSCH and SSCH to form a synchronization signal (SS) block. The MIB provides a number of RBs in the DL system bandwidth, a PHICH configuration, and a system frame number (SFN) . The physical downlink shared channel (PDSCH) carries user data, broadcast system information not transmitted through the PBCH such as system information blocks (SIBs) , and paging messages.

As illustrated in FIG. 2C, some of the REs carry demodulation reference signals (DM-RS) for channel estimation at the base station. The UE may additionally transmit sounding reference signals (SRS) in the last symbol of a subframe. The SRS may have a comb structure, and a UE may transmit SRS on one of the combs. The SRS may be used by a base station for channel quality estimation to enable frequency-dependent scheduling on the UL.

FIG. 2D illustrates an example of various channels within an UL subframe of a frame. A physical random access channel (PRACH) may be within one or more subframes within a frame based on the PRACH configuration. The PRACH may include six consecutive RB pairs within a subframe. The PRACH allows the UE to perform initial system access and achieve UL synchronization. A physical uplink control channel (PUCCH) may be located on edges of the UL system bandwidth. The PUCCH carries uplink control information (UCI) , such as scheduling requests, a channel quality indicator (CQI) , a precoding matrix indicator (PMI) , a rank indicator (RI) , and HARQ ACK/NACK feedback. The PUSCH carries data, and may additionally be used to carry a buffer status report (BSR) , a power headroom report (PHR) , and/or UCI.

FIG. 3 is a block diagram of a base station 310 in communication with a UE 350 in an access network. In the DL, IP packets from the EPC 160 may be provided to a controller/processor 375. The controller/processor 375 implements layer 3 and layer 2 functionality. Layer 3 includes a radio resource control (RRC) layer, and layer 2 includes a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The controller/processor 375 provides RRC layer functionality associated with broadcasting of system information (e.g., MIB, SIBs) , 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 functionality associated with header compression /decompression, security (ciphering, deciphering, integrity protection, integrity verification) , and handover support functions; RLC layer functionality associated with the transfer of upper layer packet data units (PDUs) , error correction through ARQ, concatenation, segmentation, and reassembly of RLC service data units (SDUs) , re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality 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 through HARQ, priority handling, and logical channel prioritization.

The transmit (TX) processor 316 and the receive (RX) processor 370 implement layer 1 functionality associated with various signal processing functions. Layer 1, which includes a physical (PHY) layer, may include error detection on the transport channels, forward error correction (FEC) coding/decoding of the transport channels, interleaving, rate matching, mapping onto physical channels, modulation/demodulation of physical channels, and MIMO antenna processing. The TX processor 316 handles mapping to signal constellations 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 coded and modulated symbols may then be split into parallel streams. Each stream may then be mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially precoded to produce multiple spatial streams. Channel estimates from a channel estimator 374 may be used to determine the coding and modulation scheme, as well as for spatial processing. The channel estimate may be derived from a reference signal and/or channel condition feedback transmitted by the UE 350. Each spatial stream may then be provided to a different antenna 320 via a separate transmitter 318TX. Each transmitter 318TX may modulate an RF carrier with a respective spatial stream for transmission.

At the UE 350, each receiver 354RX receives a signal through its respective antenna 352. Each receiver 354RX recovers information modulated onto an RF carrier and provides the information to the receive (RX) processor 356. The TX processor 368 and the RX processor 356 implement layer 1 functionality 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 by the RX processor 356 into a single OFDM symbol stream. The RX processor 356 then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT) . The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, 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 channel estimates computed by the channel estimator 358. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were 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 functionality.

The controller/processor 359 can be associated with a memory 360 that stores program codes and data. The memory 360 may be referred to as a computer-readable medium. In the UL, the controller/processor 359 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, and control signal processing to recover IP packets from the EPC 160. The controller/processor 359 is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.

Similar to the functionality described in connection with the DL transmission by the base station 310, the controller/processor 359 provides RRC layer functionality associated with system information (e.g., MIB, SIBs) acquisition, RRC connections, and measurement reporting; PDCP layer functionality associated with header compression /decompression, and security (ciphering, deciphering, integrity protection, integrity verification) ; RLC layer functionality associated with the transfer of upper layer PDUs, error correction through ARQ, concatenation, segmentation, and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

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

The UL transmission is processed at the base station 310 in a manner similar to that described in connection with the receiver function at the UE 350. Each receiver 318RX receives a signal through its respective antenna 320. Each receiver 318RX recovers information modulated onto an RF carrier and provides the information to a RX processor 370.

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

FIG. 4A is a diagram of a wireless communications system 400. The wireless communications system 400 may include a UE 402 configured to communicate with a network. The UE 402 may be an aspect of the UE 104 of FIG. 1 and/or the UE 350 of FIG. 3. While various aspects of the present disclosure are described with respect to implementation by a UE, one of ordinary skill will understand that the operations presented herein may be practiced in another type of wireless communications device, such as a base station (e.g., an eNB) .

The network may include at least one base station 460. The base station 460 may be, for example, an eNB, a gNB, a mmW base station, or another type of wireless base station. The base station 460 may be an aspect of the base station 102 or the mmW base station 180 of FIG. 1 and/or the base station 310 of FIG. 3.

In various aspects, the UE 402 may include at least an application layer 420 and a radio protocol stack 404. The radio protocol stack 404 for the UE 402 is shown with three layers: Layer 1, Layer 2, and Layer 3, which may be part of the access stratum (AS) . The Layer 1 (L1 layer) is the lowest layer and implements various PHY layer signal processing functions. The L1 layer is referred to herein as the PHY layer 406. In aspects, a modem may implement at least a portion of the operations associated with the PHY layer 406. The Layer 2 (L2 layer) is above the PHY layer 406 and is responsible for the link between the UE 402 and base station 460 over the PHY layer 406.

In the user plane, the L2 layer includes a MAC layer 410, an RLC layer 412, and a PDCP layer 414. In aspects, a baseband processor may implement one or more of the MAC layer 410, RLC layer 412, and/or PDCP layer 414 of the L2 layer (a baseband processor may also implement at least a portion of the PHY layer 406) . The L2 layer may cause various operations that affect the PHY layer 406.

The PDCP layer 414 provides multiplexing between different radio bearers and logical channels. The PDCP layer 414 also provides header compression for upper layer data packets to reduce radio transmission overhead, security by ciphering the data packets, and handover support for the UE 402 between base stations (e.g., including the base station 460) . The RLC layer 412 provides segmentation and reassembly of upper layer data packets, retransmission of lost data packets, and reordering of data packets to compensate for out-of-order reception due to HARQ. The MAC layer 410 provides multiplexing between logical and transport channels. The MAC layer 410 is also responsible for allocating the various radio resources (e.g., resource blocks) in one cell among UEs (including the UE 402) . The MAC layer 410 is also responsible for HARQ operations.

In the control plane, the radio protocol stack 404 for the UE 402 is substantially the same for the PHY layer 406 and the L2 layer with the exception that there is no header compression function for the control plane. The control plane also includes an RRC layer 418 in Layer 3 (L3 layer) . The RRC layer 418 is responsible for obtaining radio resources (e.g., radio bearers) and for configuring the lower layers using RRC signaling between the UE 402 and the base station 460.

At the UE 402, an application layer 420 terminates the end of a connection (e.g, , a connection between the UE 402 and the base station 460 (although the connection may also be established with a far-end UE, server, a Wi-Fi AP, or another wireless communications system) . Although not shown, the UE 402 may have several other layers below the application layer 420, such as a network layer (e.g., IP layer) and/or an NAS layer, which may be included in the radio protocol stack 404.

According to aspects, communication may be initiated and reflected at the application layer 420. The application layer 420 may be configured to generate and receive data that is passed down and up the radio protocol stack 404 for transmission/reception over a RAN (e.g., communication with the base station 460) . The application layer 420 may include one or more applications (e.g., the application 422) configured to generate, display, or otherwise process data as both the initial point and terminal point for such data. In aspects, a processor (e.g., an application processor) may implement at least a portion of the application layer 420.

In one aspect, the application layer 420 may include an application (e.g., the application 422) that serves as point of origination and/or destination for data sent and/or received over a RAN. Examples of the application 422 may include a web browser, a social media application, a messaging application (e.g., rich communication services (RCS) ) , a multimedia application (e.g., a streaming video application) , a gaming application, a voice or video application (e.g., voice-over-IP (VoIP) , voice-over-LTE (VoLTE) , video-over-LTE (ViLTE) , an IP multimedia subsystem (IMS) ) , or any other application that originates and/or terminates data communicated over a RAN. In another aspect, the application 422 may operate in association with one of the aforementioned exemplary applications. For example, the application 422 may be a utility application and/or a plug-in application, which may communicate or integrate with one of the aforementioned exemplary applications (although not necessarily) .

In some aspects, the application 422 may be a real-time application. A real-time application may be an application in which the user experience is provided (or attempted to be provided) immediately or currently. Therefore, the application 422 may be delay-sensitive, requiring a relatively short delay with a relatively minimal delay variation. Real-time requirements may present design issues at layers below the application layer, such as the PHY layer 406. In particular, a latency issue may appreciably affect the user experience, such as when an online mobile game lags or repeatedly pauses due to issues originating at lower layers of the radio protocol stack 404.

In order to satisfy delay-sensitivity requirements, quality of service (QoS) differentiation may be implemented at the network. For different QoSs, separate streams may be used to transport data of different services. To support different QoSs, streams of different characteristics may be mapped to different bearers. A bearer may be a unit of QoS control, and one bearer may be used to fulfill one set of QoS.

In LTE and/or other wireless communications standards (e.g., 5G NR) , a parameter called the QoS Class Identifier (QCI) may be used. The QCI defines a unique expected treatment of a bearer and is intended to provide similar handling of bearers of the same QCI, e.g., even if network nodes (e.g., the base station 460) are developed by different manufacturers. Based on a received QCI value, each network node (e.g., the base station 460) knows how a given bearer is to be treated. QCI values may be specified within a 3GPP standard so that each vendor knows expected characteristics for a bearer with a given QCI value. The characteristics may include priority level, delay budget, packet loss rate, and so on.

According to one or more wireless communications standards (e.g., 3GPP standards) , QoS may be handled at a network side (e.g., at the base station 460) , for example, as opposed to a UE side (e.g., the UE 402) . In some instances, the core network may not invoke the QoS for some flows and as such the base station 460 does not provide a specific and/or may not follow the expected characteristics for the real-time applications. Moreover, the base station 460 may provide “best effort” service (e.g., the base station 460 may not provide any guarantees that the UE 402 will be provided a certain QoS) . For example, when a network is congested, a packet delay budget or requirement may be unsatisfied. Even with QCI defined in a 3GPP standard, the application 422 may lack a reliable mechanism to cause the base station 460 to set up a transport layer with characteristics required for communication of delay-sensitive traffic (e.g., user datagram protocol (UDP)) . Rather, the base station 460 may set up a transport layer for delay-insensitive traffic where reliability is prioritized over low latency (e.g., transport control protocol (TCP) ) .

In view of the foregoing, the UE 402 may benefit from one or more mechanisms to reduce latency that is experienced by the application 422. For example, the UE 402 may perform various operations to reduce latency associated with UDP traffic, as UDP traffic is frequently associated with real-time applications. One or more layers of the radio protocol stack 404 may perform these various operations, either individually or in coordination. For example, with the help of the application layer 420, the PHY layer 406 may determine that the UE 402 is configured to execute a real-time application 422 and may switch to a mode associated with low latency. In such a mode, the UE 402 may cause one bearer (e.g., a default bearer) or all of its bearers to behave like a dedicated bearer that would provide a certain QoS even when the UE 402 has not been provided such a dedicated bearer. Thus, the UE 402 may cause low latency to be prioritized over reliability. The UE may provide specific treatment to a flow within a bearer, a complete bearer or a set of bearers.

When the UE 402 is communicating conventional traffic (e.g., non-delay-sensitive traffic) , the protocol stack 404 may conventionally operate (e.g., the UE 402 may operate according to a standard defined by one or more 3GPP technical specifications) . In various aspects, the UE 402 may determine that the UE 402 is to operate in a low-latency mode.

In one aspect, the application layer 420 may determine that the UE 402 is to operate in the low-latency mode, e.g., because the application 422 is communicating delay-sensitive traffic. The application layer 420 may be configured to indicate, to the protocol stack 404, that the protocol stack 404 is to operate in a low-latency mode. For example, the application layer 420 may inform the modem framework which in turn may inform the AS layer (e.g., including the protocol stack 404) that the application 422 is communicating delay-sensitive traffic and, therefore, the protocol stack 404 is to be configured to operate in a low-latency mode.

When the application layer 420 determines that the application 422 is no longer communicating delay-sensitive traffic, the application layer 420 may inform the AS layer that the protocol stack 404 is to be configured to return to conventional operation (e.g., by adhering to a 3GPP standard) .

In one aspect, the application layer 420 may specify a delay budget. The delay budget may be a value (e.g., duration of time) or a qualitative representation of the time that the application layer 420 expects to receive or transmit packets from the lower layers of the radio protocol stack 404, e.g., so that the application 422 may provide a continuous and/or uninterrupted user experience (e.g., smooth and seamless voice/video calling, responsive online gaming, etc. ) . The delay budget may be indicated separately for the uplink and downlink directions. Some applications may require low latency in only one direction, for instance to deliver a downlink real-time stream.

The application layer 420 may provide the delay budget to a layer of the radio protocol stack 404. The protocol stack 404 may be configured to communicate data (e.g., packets) with the application layer 420 within the delay budget. For example, the application layer 420 may indicate a delay budget of 100 milliseconds (ms) or “very low latency” . In various aspects, the application layer 420 may specify the delay budget at runtime of the application 422.

The application layer 420 may inform the AS layer via the Modem Control Interface (MCI) . For example, the application layer 420 may indicate, to the AS layer via the MCI, that the protocol stack 404 is to operate in the low-latency mode. Additionally, or alternatively, the application layer 420 may indicate, to the AS layer via the QMI, that the protocol stack 404 is to operate within a defined delay budget (e.g., 100 ms) , for a specific direction.

In one aspect, at least one layer of the protocol stack 404 (e.g., a modem of the UE 402 at the PHY layer 406) may determine that the UE 402 is to operate in the low-latency mode. For example, the PHY layer 406 (e.g., the modem) may detect at least one of a transport protocol (e.g., UDP) associated with traffic of the application 422, a network address associated with traffic of the application 422, or a destination port associated with traffic of the application 422. Based on the detection of the at least one of the transport protocol, the network address, and/or the destination port, the PHY layer 406 may determine that the UE 402 is to operate in the low-latency mode.

When the UE 402 determines that the UE 402 is to operate in the low-latency mode, the UE 402 may configure at least one layer of the protocol stack 404 to operate in the low-latency mode. Accordingly, the UE 402 may communicate with the network (e.g., the base station 460) through the configured at least one layer, e.g., in order to reduce latency experienced by the application layer 420.

In one aspect, the at least one layer may include the MAC layer 410. The MAC layer 410 may send a BSR, e.g., in order to elicit an uplink grant of a size suitable for an amount of data to be transmitted by the UE 402 to the base station 460. The MAC layer 410 may include a BSR retransmission timer. The BSR retransmission timer may define a duration for which the MAC layer 410 is to wait before resending a BSR (e.g., because the MAC layer 410 determines that an uplink grant of a suitable size is unreceived from the base station 460 in response to a BSR transmission) . Conventionally, the BSR retransmission timer may be of a first duration (e.g., 320 ms) defined by a 3GPP standard and/or the base station 460 (e.g., via RRC signaling) . The MAC layer 410 may configure the BSR retransmission timer from the first duration to a second duration. The second duration may be shorter (i.e., less) than the first duration. The second duration may be determined by the UE 402, for example, based on the delay budget (or a remaining amount of the delay budget) or based on a predetermined value. Accordingly, the MAC layer 410 may cause a BSR to be resent based on expiration of the BSR retransmission timer configured with the second duration, e.g., when an uplink grant of the suitable size is unreceived before expiration of the BSR retransmission timer.

In one aspect, the BSR retransmission timer may be dynamically configured at runtime. For example, the second duration may be determined based on the time spent between a scheduling request (SR) and an SR grant. In general at each step, the setting of the parameter governing low latency operation is done according with the remaining delay budget, which is computed as delay budget minus total queuing time experience by the packet. In some instances the queuing time can be approximated by summing the time between packet arrival at the modem layer and time when SR request is issued, SR request to grant for BSR, Time from BSR to data grant, time from first RLC TX to RLC Retx. If the UE 402 retransmits the SR, then the second duration may be aggressively reduced in order to adhere to the delay budget. For example, the second duration may be based on the difference between the delay budget and the amount of time consumed for SR transmission/retransmission and B SR grant reception. This consumption of the delay budget may propagate to other layers (e.g., RLC layer 412 and/or PDCP layer 414) so that the other layers may be dynamically configured to adjust values (e.g., thresholds, timer durations, etc. ) in order to adhere to the delay budget.

The MAC layer 410 may include a plurality of HARQ processes 430a-c, configured to manage HARQ feedback for information sent to the base station 460. HARQ feedback may be carried on a PHICH.

A transport block (TB) including a BSR may be sent on a first HARQ process 430a. When the TB including the BSR is successfully received by the base station 460, the MAC layer 410 may receive, from the base station 460, an ACK message 448 on the first HARQ process 430a. When the TB including the BSR is unsuccessfully received by the base station 460, then the MAC layer 410 may receive, from the base station 460, a NACK message 446 on the first HARQ process 430a. For a number n of transmissions/retransmissions of a TB including the BSR, the MAC layer 410 may receive n NACK messages.

The number n of NACK messages 446 received responsive to a TB including the BSR may be compared to a predetermined threshold. The predetermined threshold may be determined by the UE 402, and may be less than a threshold amount corresponding to a maximum number of HARQ retransmissions specified by the base station 460 and/or by a 3GPP standard.

In order to satisfy the delay budget, the BSR may be quickly retransmitted based on comparison of the number n of NACK messages 446 received in response to a TB including the BSR. If the number n of NACK messages 446 meets or exceeds the predetermined threshold, then the BSR may be transmitted on the next available HARQ process. For example, the MAC layer 410 may create a new TB including the BSR, and perform the transmission of the new TB including the BSR on the next available HARQ process (e.g., the second HARQ process 430b) . While this new TB may cause two BSRs to be contemporaneously transmitted over the air, this new TB may provide diversity for the BSR to increase the probability the base station 460 will receive the BSR.

Based on data provided by the application 422, the UE 402 may send PDUs 442a-c to the base station 460. In aspects, the PDUs 442a-c may be included in TBs and may be sent on a plurality of HARQ processes 430a-c -e.g., a first PDU 442a may be sent on a first HARQ process 430a, a second PDU 442b may be sent on a second HARQ process 430b, a third PDU 442c may be sent on a third HARQ process 430c. Each HARQ process 430a-c may manage HARQ feedback for a respective PDU of the PDUs 442a-c. When a first PDU 442a is successfully received by the base station 460, the MAC layer 410 may receive, from the base station 460, an ACK message 448 on a first HARQ process 430a. When a second PDU 442b is unsuccessfully received by the base station 460, the MAC layer 410 may receive, from the base station 460, one or more NACK messages 446 on the second HARQ process 430b (e.g., a NACK message 446 for each unsuccessful transmission of the second PDU 442b) . The advantage of this method is that the latency of RLC control loop, used to request retransmission, is reduced. The disadvantage is that un-necessary retransmissions may occur.

In one aspect, the at least one layer configured for the low-latency mode may include the RLC layer 412. In some aspects, the at least one layer configured for the low-latency mode may further include the MAC layer 410. In aspects, the MAC layer 410 may cause transmission of PDU 442a-c, which may include RLC PDUs. At the MAC layer 410, the PDUs 442a-c may be included in respective TBs.

The MAC layer 410 may compare, to a predetermined threshold, a number x of NACK messages 446 received by the MAC layer 410 on a first HARQ process 430a based on x transmissions/retransmissions of one or more TBs including a first PDU 442a. The predetermined threshold may be less than a threshold amount corresponding to maximum number of HARQ retransmissions specified by the base station 460 and/or by a 3GPP standard. In one aspect, the predetermined threshold may be one. In various aspects, the number x may be determined based on the delay budget (e.g., how much of the delay budget remains after a portion of the delay budget is consumed by earlier operations) .

In order to satisfy the delay budget, the first PDU 442a may be quickly retransmitted based on comparison of the number x of NACK messages 446 received in response to x transmissions/retransmissions of TB (s) including the first PDU 442a. If the number x of NACK messages 446 meets or exceeds the predetermined threshold, then the first PDU 442a may be sent on the next available HARQ process. For example, the MAC layer 410 may create a new TB including the first PDU 442a, and cause transmission of the new TB including the first PDU 442a on the next available HARQ process (e.g., the second HARQ process 430b) .

In one aspect, the at least one layer configured for the low-latency mode may include the RLC layer 412. The RLC layer 412 may be configured for polling, which may allow the RLC layer 412 to elicit, from the base station 460, a status report indicating a status of reordering buffer at the base station 460. For example, the RLC layer 412 may set a bit in one of the PDUs 442a-c in order to request the status report. Based on this status report, the RLC layer 412 may identify gaps (e.g., missing PDUs of the PDUs 442a-c) , for example, in order to determine which PDU (s) of the PDUs 442a-c are to be retransmitted.

The RLC layer 412 may be associated with an RLC poll retransmission timer that defines when the polling is allowed. For example, when the RLC poll retransmission timer is running, the RLC layer 412 may be prohibited from requesting the status report. When then the RLC poll retransmission timer is expired, the RLC layer 412 may be allowed to request the status report.

Conventionally, the RLC poll retransmission timer may be of a first duration defined by a 3GPP standard and/or the base station 460 (e.g., via RRC signaling) . The RLC layer 412 may configure the RLC poll retransmission timer from the first duration to a second duration. The second duration may be shorter than the first duration. The second duration may be determined by the UE 402, for example, based on the delay budget (or a remaining amount of the delay budget, c. f. para 85) or based on a predetermined value. Accordingly, the RLC layer 412 may request a status report at expiration of the RLC poll retransmission timer configured with the second duration. The RLC poll retransmission timer configured with the second duration may allow the RLC layer 412 to more frequently request the status report than if the RLC poll retransmission timer were configured with the first duration. The more frequent status report may allow an acknowledged mode (AM) window associated with HARQ feedback to advance more quickly, e.g., because the UE 402 may retransmit any missing PDUs of the PDUs 442a-c more quickly. This method effectively lowers the latency while avoiding un-necessary RLC retransmission, which consume bandwidth un-necessarily.

Based on data to be provided to the application 422, the UE 402 may receive PDUs 440a-c from the base station 460. In aspects, the received PDUs 440a-c may be included in TBs and may be received on a plurality of HARQ processes 430a-c -e.g., a first PDU 440a may be received on a first HARQ process 430a, a second PDU 440b may be received on a second HARQ process 430b, a third PDU 440c may be received on a third HARQ process 430c. Each HARQ process 430a-c may manage HARQ feedback for a respective PDU of the received PDUs 440a-c. When a first PDU 440a is successfully received by the UE 402, the MAC layer 410 may send, to the base station 460, an ACK message 450 on a first HARQ process 430a. When a second PDU 440b is unsuccessfully received by the UE 402, the MAC layer 410 may send, to the base station 460, one or more NACK messages 444 on the second HARQ process 430b.

In one aspect, the at least one layer configured for the low-latency mode may include the RLC layer 412. The RLC layer 412 may include an AM reception window 432. The received PDUs 440a-c may be managed in the AM reception window 432. For example, the RLC layer 412 may reorder received PDUs 440a-c in the AM reception window 432, e.g., based on a respective sequence number (SN) associated with a respective one of the received PDUs 440a-c. The AM reception window 432 may be updated so that the lower edge of the AM reception window 432 is equal to an SN of the next in-order PDU, e.g., the first PDU 440a with the lowest SN respective to the SNs of the other PDUs 440b-c. Reordering of the received PDUs 440a-c in the AM reception window 432 may allow in-order delivery of data included in the received PDUs 440a-c to the higher layers (e.g., the application layer 420) but may require additional time in order to successfully receive all the PDUs.

In aspects, the RLC layer 412 in a transmitter may be configured to detect one or more missing PDUs. For example, the RLC layer 412 may determine that a second PDU 440b is unreceived (e.g., at least one NACK message 444 may be transmitted on the second HARQ process 430b associated with the second PDU 440b) . For example, the second PDU 440b having a second SN between the first SN of the first PDU 440a and the third SN of the third PDU 440c may be determined to be missing. When the second PDU 440b is unreceived at the receiver, the RLC layer 412 may request the missing second PDU 440b. For example, the RLC layer 412 at the receiver may cause transmission of a status report indicating the second SN corresponding to the missing second PDU 440b. In an aspect, the RLC layer 412 at the transmitter may transmit a PDU (e.g., the third PDU 440c) having at least one bit set indicating a request for the status report from the RLC at the receiver.

The RLC layer 412 at the receiver may be associated with an RLC transmission reordering timer that defines when the status report indicating the missing second PDU 440b is allowed. For example, when the RLC transmission reordering timer is running, the RLC layer 412 may be prohibited from sending the status report. When then the RLC transmission reordering timer is expired, the RLC layer 412 may be allowed to send the status report.

Conventionally, the RLC transmission reordering timer may be of a first duration defined by a 3GPP standard and/or the base station 460 (e.g., via RRC signaling) . The RLC layer 412 may configure the RLC transmission reordering timer from the first duration to a second duration. The second duration may be shorter than the first duration. In one aspect, the UE 402 may determine the second duration based on the delay budget (or a remaining amount of the delay budget) . In another aspect, the UE 402 may determine the second duration based on a predetermined value. In one aspect, the predetermined value may be 0 so that the RLC layer 412 does not wait to send the status report requesting the missing second PDU 440b, but instead immediately sends the status report when the second PDU 440b is determined to be missing.

In aspects, the RLC layer 412 may send a status report requesting the missing second PDU 440b at expiration of the RLC transmission reordering timer configured with the second duration. The RLC transmission reordering timer configured with the second duration may allow the RLC layer 412 to more frequently send the status report indicating missing PDU (s) than if the RLC transmission reordering timer were configured with the first duration. The more frequent sending of the status report may elicit the missing second PDU 440b more quickly than ifthe RLC transmission reordering timer were configured with the first duration.

In one aspect, the at least one layer configured for the low-latency mode may include the RLC layer 412. The AM reception window 432 may be configured with a highest expected SN (e.g., a VR_H value, as defined by a 3GPP standard) , which may correspond to the highest SN allowed in the AM reception window 432. When an SN of the most recently received PDU corresponds to or is equal to the highest expected SN, then any missing PDUs may be stale and, therefore, may not be useful to the application 422. Thus, for the low-latency mode, the application 422 may benefit from advancement of the AM reception window 432 in order to continue real-time operation, even without the missing PDU. For example, if the RLC layer 412 receives the third PDU 440c having a third SN corresponding to the highest expected SN, then the missing second PDU 440b may be already stale and the RLC layer 412. Depending on the configuration the RLC layer may refrain from delivering or proceed to delivering data of that second PDU 440b to the higher layers.

As described, supra, the RLC layer 412 may determine that at least one PDU (e.g., the second PDU 440b) is missing or absent. For example, the RLC layer 412 may receive the third PDU 440c having a third SN, and the third SN may correspond to the highest expected SN (e.g., VR_H) . The second PDU 440b may be missing or absent (e.g., the RLC layer 412 may determine that the second PDU 440b having the second SN is unreceived when the third PDU 440c having the third SN is received) .

Because the second PDU 440b may be now considered stale, the RLC layer 412 may “fake” an ACK message (i.e. indicate ACK instead of NACK) associated with the second PDU 440b so the base station 460 will refrain from retransmitting the second PDU 440b and will continue with transmission of PDUs having higher SNs. Optionally in addition, the RLC layer 412 may cause an ACK message 450 to be sent on the second HARQ process 430b associated with the second PDU 440b, even though the second PDU 440b is absent.

Additionally, the RLC layer 412 may deliver data associated with the received

PDUs

440a, 440c to at least one layer higher than the RLC layer 412 (e.g., the application layer 420) . For example, the RLC layer 412 may deliver data corresponding to the third PDU 440c to at least one higher layer, even though the third PDU 440c has an SN higher than the SN of the missing second PDU 440b. Thus, the RLC layer 412 may advance the AM window 432 and real-time operation of the application 422 may continue (albeit without data corresponding to the second PDU 440b) . In some alternative mode the RLC layer may later deliver an SN of lower value to the upper layer.

In one aspect, the at least one layer configured for the low-latency mode may include the RLC layer 412. In aspects, the size of the PDUs 442a-c may be associated with the size of an uplink grant provided by the base station 460. The RLC layer 412 may attempt to concatenate as many packets as possible from the higher layers (e.g., PDCP packets, which include IP packets) . If the UE 402 is initially provided a relatively large grant (e.g., two kilobytes) , the RLC layer 412 may create at least one PDU of the PDUs 442a-c having a size commensurate with the grant size. If radio conditions between the base station 460 and the UE 402 deteriorate, a PDU (e.g., the second PDU 442b) may be unreceived by the base station 460. However, the base station 460 still expects a PDU corresponding to the relatively large grant size.

In aspects, the RLC layer 412 may detect that a PDU having an SN is unreceived at the base station 460 and needs to be retransmitted by the UE 402. For example, a NACK message 446 may be received in response to the transmission of the second PDU 442b and/or a status report may indicate a second SN corresponding to the second PDU 442b is missing. Similar to stale received PDUs, transmitted (e.g., uplink) PDUs may be stale with respect to real-time operation of the application 422. Thus, the RLC layer 412 may attempt to advance an AM window at the base station 460 in order to continue real-time operation.

In various aspects, the RLC layer 412 may determine a second PDU 442b is unreceived by the base station 460 -e.g., at least one NACK message 446 may be received based on at least one transmission of a TB including the second PDU 442b. The second PDU 442b may be associated with a second SN and may include information associated with the application 422.

If the second PDU 442b is not timely received by the base station 460, then the second PDU 442b may be stale and may be preventing real-time operation. Thus, the UE 402 may “forge” another version of the unreceived second PDU 442b, using the second SN, in order to allow the base station 460 to deliver PDUs with higher SNs to higher layers of the base station 460 and advance an AM window of the base station 460. When radio conditions deteriorate, a smaller PDU may be more likely to be received by the base station 460. Therefore, the RLC layer 412 may generate a “forged” PDU having a relatively small amount of data (e.g., relative to the grant size and/or relative to the size of the data included in the second PDU 442b) . However, the “forged” PDU may include the same SN as the second PDU 442b. The RLC layer 412 may then send the “fake” PDU having the same SN as the second PDU 442b but a relatively small amount of data. The forged PDU may include the original PDCP PDU headers, with reduced PDCP payloads. Including the PDCP PDU headers ensures the PDCP operation continues without waiting for associated PDCP PDUs.

In one aspect, the at least one layer configured for the low-latency mode may include the PDCP layer 414. The PDCP layer 414 may include a discard timer (or drop timer) . For each PDCP PDU, received from a higher layer, the PDCP layer 414 may start the discard timer. When the UE 402 has not initiated transmission of the PDCP PDU upon expiration of the discard timer, then the PDCP PDU is discarded. This mechanism may prevent excessive delays and/or queuing.

Conventionally, the PDCP discard timer may be of a first duration defined by a 3GPP standard and/or the base station 460 (e.g., via RRC signaling) . The PDCP layer 414 may configure the PDCP discard timer from the first duration to a second duration. The second duration may be shorter than the first duration. In one aspect, the UE 402 may determine the second duration based on the delay budget (or a remaining amount of the delay budget) . In another aspect, the UE 402 may determine the second duration based on a predetermined value. The UE may selectively apply the reduced discard timer only to specific PDCP SDUs within a bearer. For instance to the UDP packets.

In one aspect, the at least one layer configured for the low-latency mode may include the RLC layer 412 and/or the MAC layer 410. As described, supra, the MAC layer 410 has a plurality of HARQ processes 430a-c. In an aspect, the first HARQ process 430a may experience more success than the second HARQ process 430b -e.g., at least one ACK message 450 may be sent on the third HARQ process 430c in response to a TB including the third PDU 440c, while at least one NACK message 444 may be sent on the second HARQ process 430b in response to an unreceived TB including the second PDU 440b. Thus, the second HARQ process 430b may experience some failure of reception or decoding, which may cause PDUs to become stale. In order to continue real-time operation of the application 422, the third PDU 440c should be delivered to the higher layers even when the second PDU 440b is unreceived.

Accordingly, the MAC layer 410 may determine that the third PDU 440c, received on the third HARQ process 430c, includes a third SN that is higher than a second SN associated with the second PDU 440b, which may be received on the second HARQ process 430b. Therefore, the MAC layer 410 may send an ACK message 450 on the second HARQ process 430b even when a TB including the second PDU 440b is unreceived.

Additionally, the MAC layer 410 and RLC layer 412 may deliver data associated with the received PDU 440c to at least one layer higher than the RLC layer 412 (e.g., the application layer 420) . For example, the RLC layer 412 may deliver data corresponding to the third PDU 440c to at least one higher layer, even though the third PDU 440c has an SN higher than the SN of the missing second PDU 440b. Thus, real-time operation of the application 422 may continue (albeit without data corresponding to the second PDU 440b) . The RLC layer 412 may deliver the third PDU 440c (and other PDUs having higher SNs) , for example, without waiting for reordering with respect to the missing second PDU 440b.

In an aspect, the UE 402 may refrain from sending an ACK message (described just above) based on an unreceived TB when the UE 402 is in a handover preparation state. For example, if a measurement report is sent by the UE 402 within a threshold period of time, the MAC layer 410 may refrain from sending an ACK message when a NACK message should be sent in response to an unreceived TB, to guarantee proper reception of a putative handover command.

In one aspect, the at least one layer configured for the low-latency mode may include the MAC layer 410. The MAC layer 410 may include at least one timer associated with a power headroom report (PHR) . For example, the MAC layer 410 may include a PHR prohibit timer or a periodic PHR timer. A timer associated with a PHR may indicate when the MAC layer 410 is allowed to send a PHR. For example, when the timer is running, the MAC layer 410 may be prohibited from sending a PHR. When the timer expires, the MAC layer 410 may send a PHR.

Conventionally, the timer associated with a PHR may be of a first duration defined by a 3GPP standard and/or the base station 460 (e.g., via RRC signaling) . The MAC layer 410 may configure the timer associated with PHR from the first duration to a second duration. The second duration may be shorter than the first duration. In one aspect, the UE 402 may determine the second duration based on the delay budget (or a remaining amount of the delay budget) . In another aspect, the UE 402 may determine the second duration based on a predetermined value.

In one aspect, the at least one layer configured for the low-latency mode may include the MAC layer 410. The MAC layer 410 may be configured to send a PHR based on a path loss change threshold (e.g., dl-PathlossChange) . The UE 402 may detect a path loss and send a PHR when the detected path loss satisfies (e.g., meets or exceeds) the path loss change threshold.

Conventionally, the path loss change threshold may be of a first value defined by a 3GPP standard and/or the base station 460 (e.g., via RRC signaling) . The MAC layer 410 may configure the path loss change threshold from the first value to a second value. The second value may be less than the first value. In one aspect, the UE 402 may determine the second value based on the delay budget (e.g., a lower delay budget and/or lower remaining delay budget may necessitate sending the PHR at a lesser path loss change) . In another aspect, the UE 402 may determine the second value based on a predetermined value.

In one aspect, the at least one layer configured for the low-latency mode may include the PHY layer 406. The PHY layer 406 may transmit signals (e.g., including the PDUs 442a-b) to the base station 460 using a transmit power.

Conventionally, the transmit power may be of a first value defined by a 3GPP standard and/or the base station 460 (e.g., via RRC signaling) . The PHY layer 406 may configure the transmit power from the first value to a second value. The second value may be greater than the first value. In one aspect, the UE 402 may determine the second value based on the delay budget (e.g., lower delay budget may necessitate greater transmit power) . In another aspect, the UE 402 may determine the second value based on a predetermined value.

In one aspect, the at least one layer configured for the low-latency mode may include the MAC layer 410. The MAC layer 410 may include a timer associated with an SR. The timer associated with an SR (e.g., sr-ProhibitTimer) may indicate when the MAC layer 410 is allowed to send (or resend) an SR. For example, when the timer is running, the MAC layer 410 may be prohibited from sending an SR. When the timer expires, the MAC layer 410 may send (or resend) an SR.

Conventionally, the timer associated with an SR may be of a first duration defined by a 3GPP standard and/or the base station 460 (e.g., via RRC signaling) . The MAC layer 410 may configure the timer associated with SR from the first duration to a second duration. The second duration may be shorter than the first duration. In one aspect, the UE 402 may determine the second duration based on the delay budget (or a remaining amount of the delay budget) . In another aspect, the UE 402 may determine the second duration based on a predetermined value. The UE may determine to use the second duration based on whether the queued traffic requires low latency.

In one aspect, the at least one layer configured for the low-latency mode may include the MAC layer 410. The MAC layer 410 may be configured to release a PUCCH resource (e.g., PUCCH-SR resource) after a threshold number of failed attempts to receive an uplink grant in response to an SR (e.g., dsr-TransMax) .

Conventionally, the threshold number of failed attempts to receive an uplink grant in response to an SR may be of a first value defined by a 3GPP standard and/or the base station 460 (e.g., via RRC signaling) . The MAC layer 410 may configure the threshold number of failed attempts to receive an uplink grant in response to an SR from the first value to a second value. The second value may be greater than the first value. In one aspect, the UE 402 may determine the second value based on the delay budget (e.g., a lower delay budget may necessitate a larger threshold so that the UE 402 may receive an uplink grant) . In another aspect, the UE 402 may determine the second value based on a predetermined value.

As described with respect to the BSR retransmission timer, supra, one or more of the values (e.g., durations, thresholds, transmit power values, etc. ) configured by the at least one layer that is configured to operate in the low-latency mode may be dynamically configured, e.g., configured at runtime. For example, the application layer 420 may provide a delay budget that the one or more layers of the protocol stack 404 dynamically adjust to operate within. For example, if the BSR retransmission timer is reduced (e.g., because the uplink grant is not timely received) , then the delay budget may be reduced for other layers and/or for other operations because a portion of the delay budget is consumed by one or more BSR retransmissions. Further to such an example, the RLC poll retransmission timer may be aggressively reduced because a portion of the delay budget was consumed by the BSR retransmission (s) . Alternatively or additionally, the threshold number of NACK messages received before retransmission of an RLC PDU on a different HARQ process may be reduced in order to adhere to the delay budget. In contrast, for example, the RLC poll retransmission timer and/or threshold number of NACK messages may be less aggressively reduced (or unreduced) when the uplink grant responsive to the BSR is timely received (e.g., because the delay budget is unconsumed by BSR retransmissions) .

In one aspect, the at least one layer configured for the low-latency mode may include the RLC layer 412. The RLC layer 412 may be configured for polling, which may allow the RLC layer 412 to elicit, from the base station 460, a status report, for example, indicating RLC PDU (s) that are unreceived by the base station 460. For example, the RLC layer 412 may set a polling bit in one of the PDUs 442a-c in order to request the status report. Based on this status report, the RLC layer 412 may identify gaps (e.g., missing PDUs of the PDUs 442a-c) , for example, in order to determine which PDU (s) of the PDUs 442a-c are to be retransmitted.

If, however, an RLC PDU having the polling bit set to elicit the status report is unreceived by the base station 460, the UE 402 may be unable to identify RLC PDUs that are to be retransmitted. Accordingly, the RLC layer 412 may resend at least one RLC PDU, e.g., even when unprompted responsive to a status report of NACK feedback.

In various aspects, the RLC layer 412 may send at least a first RLC PDU 442a having a first SN. When the RLC layer 412 sends the first RLC PDU 442a, the RLC layer 412 may begin an RLC timer. In various aspects, the RLC timer may have a duration that is based on the delay budget. For example, the RLC layer 412 may dynamically adjust the duration of the RLC timer in order to provide continuous service during the low-latency mode. Thus, when a relatively smaller amount of the delay budget has been consumed prior to sending the first RLC PDU 442a, then the RLC layer 412 may set the duration of the RLC timer to a relatively longer duration. Correspondingly, when a relatively larger amount of the delay budget has been consumed prior to sending the first RLC PDU 442a, then the RLC layer 412 may set the duration of the RLC timer to a relatively shorter duration.

After sending the first RLC PDU 442a, the RLC layer 412 may expect ACK/NACK feedback responsive to the first RLC PDU 442 (e.g., ACK message 448 or NACK message 446) . At expiry of the timer, the RLC layer 412 may assume that the first PDU 442a is unreceived by the base station 460 ifthe RLC layer 412 is not provided ACK/NACK feedback for the first RLC PDU 442a. Accordingly, the RLC layer 412 may resend the first RLC PDU 442a having the first SN.

In various aspects, the RLC layer 412 may set a polling bit of the resent first RLC PDU 442a to elicit the status report from the base station 460, e.g., so that the RLC layer 412 may determine whether other RLC PDUs are unreceived by the base station 460.

In some aspects, the RLC layer 412 may send, after sending the first RLC PDU 442a, one or more additional RLC PDUs 442b-c having respective SNs higher than the first SN. The additional RLC PDUs 442b-c may be sent while the RLC timer is running. At expiry of the timer, the RLC layer 412 may additionally resend the one or more additional RLC PDUs 442b-c when ACK/NACK feedback is unreceived for the one or more additional RLC PDUs 442b-c. In various aspects, the RLC layer 412 may set a respective polling bit of at least one of the one or more additional RLC PDUs 442b-c that are resent to elicit the status report from the base station 460

FIG. 4B is a call flow diagram illustrating a method 430 for a RACH procedure 415. While the illustrated aspect is contention-based, the present disclosure comprehends aspects in which the RACH procedure 415 is not contention-based.

In one aspect, the at least one layer configured for the low-latency mode may include the MAC layer 410. The MAC layer 410 may be configured to send an SR 403 to the base station 460, e.g., in order to elicit an uplink grant. Without an uplink grant, the MAC layer 410 may be unable to send data to the base station 460. However, an SR 403 may be unreceived by the base station 460 (e.g., due to interference or other channel conditions) , and so the UE 402 may not receive an uplink grant in response to an SR 403 include a timer associated with an SR. The MAC layer 410 may be configured with an SR retransmission threshold that specifies the number of times the MAC layer 410 is allowed to send (or resend) an SR 403. For example, when the UE 402 has resent an SR after the SR retransmission threshold, the MAC layer 410 may be prohibited from resending an SR.

Conventionally, the SR retransmission threshold may have a first value defined by a 3GPP standard and/or the base station 460 (e.g., via RRC signaling) . The MAC layer 410 may configure the SR retransmission threshold from the first value to a second value. The second value may be less than the first value -e.g., if an uplink grant is unreceived after a lower number of SR attempts, then the continuous low- latency operation may be jeopardized by continuing SR attempts up to an SR retransmission threshold configured with the first value. In one aspect, the UE 402 may determine the second value based on the delay budget (or a remaining amount of the delay budget) . In another aspect, the UE 402 may determine the second value based on a predetermined value. The UE may determine to use the second value based on whether queued traffic requires low latency.

The MAC layer 410 may attempt to elicit an uplink grant by sending one or more SRs 403a-n. Each of the SRs 403a-n may fail to elicit an uplink grant from the base station 460. If the MAC layer 410 is unable to obtain an uplink grant after sending the last SR 403n up to the SR retransmission threshold configured with the second value, then the MAC layer 410 may assume that subsequent SR attempts may be unreceived and/or that another approach to obtaining an uplink grant should be performed in order to continue providing low-latency service. Therefore, the UE 402 may perform a RACH procedure 415 in order to obtain an uplink grant.

In aspects, the UE 402 may be allocated one or more resources on a PUCCH for SR transmission (PUCCH-SR) . Conventionally, the UE 402 may be release one or more resources allocated to the UE 402 on the PUCCH for SR transmission. According to the present disclosure, the UE 402 may refrain from releasing the one or more resources allocated to the UE 402 for SR transmission on the PUCCH. That is, the UE 402 may retain a PUCCH-SR configuration provided to the UE 402 by the base station 460. The UE 402 may retain the PUCCH-SR configuration even when switching to the RACH procedure 415 in order to obtain the uplink grant. For example, the UE 402 may retain the PUCCH-SR configuration for a subsequent SR. Accordingly, the UE 402 may already have one or more resources on the PUCCH allocated for SR transmission when performing a subsequent SR transmission. The retention of the PUCCH-SR configuration for a subsequent SR transmission may be relatively quicker than releasing one or more allocated PUCCH resources for SR transmission (e.g., when switching to the RACH procedure 415) and obtaining a new PUCCH-SR configuration for a subsequent SR transmission.

First, the UE 402 may select a RACH preamble for the RACH procedure. Further, the UE 402 may determine a random access (RA) RNTI in order to identify the UE 402 during the RACH procedure. The UE 402 may determine an RA-RNTI based on, for example, a time slot number in which a MSG1 405 is sent. The UE 402 may include the RACH preamble and the RA-RNTI in the MSG1 405.

In an aspect, the UE 402 may determine at least one resource (e.g., a time and/or frequency resource) that is to carry the MSG1 405. For example, the base station 460 may broadcast system information (e.g., a SIB) , and the UE 402 may acquire the at least one resource based on the system information (e.g., system information included in a SIB2) . The UE 402 may send the MSG1 405 to the base station 460, for example, on the at least one resource. If the UE 402 does not receive a response to the MSG1 405 (e.g., after expiration of a timer) , then the UE 402 may increase transmit power (e.g., by a fixed interval) and resend the MSG 1 405.

Based on the MSG1 405, the base station 460 may send, to the UE 402, a MSG2 407. The MSG2 407 may also be known as a random access response and may be sent on a downlink shared channel (DL-SCH) . The base station 460 may determine a temporary cell RNTI (T-CRNTI) . Further, the base station 460 may determine a timing advance value so that the UE 402 may adjust timing to compensate for delay. Further, the base station 460 may determine an uplink resource grant, which may include an initial resource assignment for the UE 402 so that the UE 402 may use the uplink shared channel (UL-SCH) . The base station 460 may generate the MSG2 407 to include the C-RNTI, the timing advance value, and/or the uplink grant resource. The base station 460 may then transmit the MSG2 407 to the UE 402. In an aspect, the UE 402 may determine an uplink resource grant based on the MSG2 407.

Based on the MSG2 407, the UE 402 may send, to the base station 460, a MSG3 409. The MSG3 409 may also be known as an RRC connection request message and/or a scheduled transmission message. The UE 402 may determine a temporary mobile subscriber identity (TMSI) associated with the UE 402 or another random value used to identify the UE 402 (e.g., if the UE 402 is connecting to the network for the first time) . The UE 402 may determine a connection establishment clause, which may indicate why the UE 402 is connecting to the network. The UE 402 may generate the MSG3 409 to include at least the TMSI or other random value, as well as the connection establishment clause. The UE 402 may then transmit the MSG3 409 to the base station on the UL-SCH.

Based on the MSG3 409, the base station 460 may send, to the UE 402, a MSG4 411. The MSG4 411 may also be known as a connection resolution message. The base station 460 may address the MSG4 411 toward the TMSI or random value from the MSG3 409. The MSG4 411 may be scrambled with a C-RNTI associated with the UE 402. The base station 460 may transmit the MSG4 411 to the UE 402. The UE 402 may decode the MSG4 411, for example, using the C-RNTI associated with the UE 402. This RACH procedure may allow the UE 402 to be synchronized with a network. In aspects, the MSG4 411 may include an uplink grant. Based on the uplink grant received through the RACH procedure 415, the UE 402 may send uplink data (e.g., queued low-latency traffic) .

FIG. 5 is a flowchart of a method 500 of wireless communication. The method 500 may be performed by a wireless communications device, such as the UE 104 of FIG. 1, the UE 350 of FIG. 3, and/or the UE 402 of FIG. 4A. In other aspects, the method 500 may be practiced by another wireless communications device, such as an eNB or other base station.

In FIG. 5, various operations may be optional. Thus, the present disclosure contemplates a method 500 in which one or more operations are omitted and/or alternatively performed. Further, one or more operations of the method 500 may be transposed and/or contemporaneously performed.

At operation 502, the UE may determine that the UE is operate in a low-latency mode. For example, an application of the UE may indicate to a radio protocol stack of the UE that the application is a real-time application and, therefore, requires low latency. Based on the indication, the radio protocol stack may determine that the radio protocol stack is to operate in the low-latency mode. In the context of FIG. 4A, at least one layer of the radio protocol stack 404 may determine that the radio protocol stack 404 of the UE 402 is to be configured to operate in a low-latency mode.

In an aspect, operation 502 may include operation 520 and operation 522. At operation 520, the UE may detect, by a modem of the UE, at least one of a transport protocol associated with traffic of an application, a network address associated with traffic of an application, or a destination port associated with traffic of an application. For example, the modem may detect UDP traffic, a network address associated with a real-time application (e.g., gaming server) , and/or a destination port (e.g., UDP port) . In the context of FIG. 4A, the PHY layer 406 may detect at least one a transport protocol associated with traffic of the application 422, a network address associated with traffic of the application 422, or a destination port associated with traffic of the application 422.

At operation 522, the UE may determine, by the modem of the UE, that the UE is to operate in the low-latency mode based on the detected at least one of the transport protocol, the network address, and/or the destination port. For example, the modem may determine that the detected at least one of the transport protocol, the network address, and/or the destination port is associated with low-latency requirements, and the modem may determine that at least one layer of the radio protocol stack is to be configured for the low-latency mode. In the context of FIG. 4A, the PHY layer 406 may determine that the radio protocol stack 404 of the UE 402 is to operate in the low-latency mode based on the detected at least one of the transport protocol associated with traffic of the application 422, the network address associated with traffic of the application 422, or the destination port associated with traffic of the application 422.

Continuing to operation 504, the UE may configure at least one layer of the UE to operate in the low-latency mode. For example, the UE may identify at least one configurable variable (e.g., a threshold, a timer duration, or another value) , and the UE may configure the at least one configurable variable with a value (e.g., threshold value, duration, etc. ) associated with the low-latency mode. In an aspect, the configured value may be different from a value defined by a standard (e.g., 3GPP standard) or indicated by a network (e.g., via RRC signaling) . In the context of FIG. 4A, the radio protocol stack 404 of the UE 402 may configure at least one layer of the radio protocol stack 404 of the UE 402 to operate in the low-latency mode.

At operation 506, the UE may communicate with a network through the configured at least one layer. For example, the UE may detect a condition associated with the at least one configurable variable, and the UE may transmit data to the network when the at least one condition is satisfied -e.g., the condition may be expiration of a timer or a detected value or measurement that meets or exceeds a threshold. In the context of FIG. 4A, the UE 402 may communication with the base station 460 through the configured at least one layer of the radio protocol stack 404.

FIG. 6 illustrates an aspect of operation 504, at which at least one layer of the UE is configured to operate in the low-latency mode. In an aspect, operation 504 may include operation 602 and operation 604.

At operation 602, the UE may configure a BSR retransmission timer from a first duration to a second duration. The second duration may be shorter than the first duration. In an aspect, the first duration is configured via RRC signaling. For example, the UE may receive the first duration via RRC signaling and configure the BSR retransmission timer with the first duration. When the UE is to be configured in the low-latency mode, the UE may configure the BSR retransmission timer from the first duration to the second duration. In the context of FIG. 4A, the MAC layer 410 may configure a BSR retransmission timer from a first duration to a second duration, and the second duration may be shorter than the first duration, and the first duration may be configured via RRC signaling from the base station 460.

At operation 604, the UE may send a BSR based on expiration of the BSR retransmission timer configured with the second duration. For example, the UE may begin the BSR retransmission timer and may detect that an uplink grant is unreceived in response to a BSR at expiration of the BSR retransmission timer. Based on expiration of the BSR retransmission timer, the UE may retransmit the BSR. In the context of FIG. 4A, the MAC layer 410 may send a BSR to the base station 460 based on expiration of the BSR retransmission timer configured with the second duration.

FIG. 7 illustrates an aspect of operation 504, at which at least one layer of the UE is configured to operate in the low-latency mode. In an aspect, operation 504 may include operation 702 and operation 704.

At operation 702, the UE may compare, to a predetermined threshold, a number n of HARQ NACK messages based on n transmission of a TB including a BSR from a first HARQ process. For example, the UE may receive one or more NACK messages on a first HARQ process, and the UE may compare the one or more NACK messages to a predetermined threshold. In the context of FIG. 4A, the MAC layer 410 may compare, to a predetermined threshold, a number n of HARQ NACK messages 446 received based on n transmissions of a TB including a BSR from a first HARQ process 430a.

At operation 704, the UE may send, on a second HARQ process, the BSR in a new TB based on comparison of the number n of NACK messages to the predetermined threshold. For example, the UE may determine that the number n of NACK messages meets or exceeds the predetermined threshold, and the UE may send a BSR on a second HARQ process when the number n of NACK messages meets or exceeds the predetermined threshold. In the context of FIG. 4A, the MAC layer 410 may send, on a second HARQ process 430b, the BSR in a new TB based on comparison of the number n of NACK messages 446 to the predetermined threshold.

FIG. 8 illustrates an aspect of operation 504, at which at least one layer of the UE is configured to operate in the low-latency mode. In an aspect, operation 504 may include operation 802 and operation 804.

At operation 802, the UE may compare, to a predetermined threshold, a number x of HARQ NACK messages received based on x transmissions of a MAC TB including a first RLC PDU from a first HARQ process. For example, the UE may receive one or more NACK messages on a first HARQ process, and the UE may compare the one or more NACK messages to a predetermined threshold. In the context of FIG. 4A, the MAC layer 410 may compare, to a predetermined threshold, a number x of HARQ NACK messages 446 received based on x transmissions of a MAC TB including a first RLC PDU 442a from a first HARQ process 430a.

At operation 804, the UE may retransmit the first RLC PDU based on comparison of the number x of NACK messages to the predetermined threshold. For example, the UE may determine that the number x of NACK messages meets or exceeds the predetermined threshold, and the UE may retransmit the first RLC PDU when the number n of NACK messages meets or exceeds the predetermined threshold. In the context of FIG. 4A, the MAC layer 410 may create a new TB that includes the first RLC PDU 442a and the MAC layer 410 may send the new TB including the first RLC PDU 442a (e.g., resend the first RLC PDU 442a) , for example, on the first HARQ process 430a or on the second HARQ process 430b.

FIG. 9 illustrates an aspect of operation 504, at which at least one layer of the UE is configured to operate in the low-latency mode. In an aspect, operation 504 may include operation 902 and operation 904.

At operation 902, the UE may configure an RLC retransmission timer from a first duration to a second duration. The second duration may be shorter than the first duration. In an aspect, the first duration is configured via RRC signaling. For example, the UE may receive the first duration via RRC signaling and configure the RLC retransmission timer with the first duration. When the UE is to be configured in the low-latency mode, the UE may configure the RLC retransmission timer from the first duration to the second duration. In the context of FIG. 4A, the RLC layer 412 may configure an RLC retransmission timer from a first duration to a second duration, and the second duration may be shorter than the first duration, and the first duration may be configured via RRC signaling from the base station 460.

At operation 904, the UE may send a request for a status report from the network based on expiration of the RLC retransmission timer configured with the second duration. For example, the UE may begin the RLC retransmission timer. Based on expiration of the RLC retransmission timer, the UE may send the request for the status report. In the context of FIG. 4A, the RLC layer 412 may send a request for a status report from the network to the base station 460 based on expiration of the RLC retransmission timer configured with the second duration.

FIG. 10 illustrates an aspect of operation 504, at which at least one layer of the UE is configured to operate in the low-latency mode. In an aspect, operation 504 may include operation 1002 and operation 1004.

At operation 1002, the UE may configure an RLC transmission reordering timer from a first duration to a second duration. The second duration may be shorter than the first duration. In an aspect, the first duration is configured by the network. For example, the UE may receive the first duration from a base station and configure the RLC transmission reordering timer with the first duration. When the UE is to be configured in the low-latency mode, the UE may configure the RLC transmission reordering timer from the first duration to the second duration. In the context of FIG. 4A, the RLC layer 412 may configure an RLC transmission reordering timer from a first duration to a second duration, and the second duration may be shorter than the first duration, and the first duration may be configured by the base station 460.

At operation 1004, the UE may send a status report to the network based on expiration of the RLC transmission reordering timer configured with the second duration. For example, the UE may begin the RLC transmission reordering timer. Based on expiration of the RLC retransmission timer, the UE may send the status report. In the context of FIG. 4A, the RLC layer 412 may send a status report to the base station 460 based on expiration of the RLC transmission reordering timer configured with the second duration.

FIG. 11 illustrates an aspect of operation 504, at which at least one layer of the UE is configured to operate in the low-latency mode. In an aspect, operation 504 may include operation 1102, operation 1104, and operation 1106.

At operation 1102, the UE may determine that at least one expected RLC PDU is absent. For example, the UE may determine an RLC PDU having a first SN is received and determine that an RLC PDU having a third SN is received. The UE may determine that an RLC PDU having a second SN is unreceived based on reception of the RLC PDUs having the first and third SNs. In the context of FIG. 4A, the RLC layer 412 may determine that the second RLC PDU 440b is absent, e.g., based on reception of the first and third RLC PDUs 440a, 440c.

At operation 1104, the UE may send, based on the determination that the at least one expected RLC PDU is absent, an ACK message instead of a NACK message when an SN of a most recently received RLC PDU corresponds to a highest excepted SN (e.g., VR_H) . For example, the UE may identify the SN of a most recently received RLC PDU and the UE may compare the SN to a highest expected SN. When the SN of the most recently received RLC PDU matches the highest expected SN, the UE may send an ACK message instead of a NACK message in association with the at least one expected RLC PDU determined to be absent. In the context of FIG. 4A, the MAC layer 410 may send, based on the determination that at least one expected RLC PDU is absent, an ACK message 450 instead of a NACK message 444 when an SN of the most recently received RLC PDU (e.g., the third PDU 440c) corresponds to a highest expected SN.

At operation 1106, the UE may deliver to at least one layer higher than the RLC layer, data associated with one or more RLC PDUs. For example, the UE may extract data from one or more RLC PDUs and the UE may pass the extracted data up the radio protocol stack to the application layer. In the context of FIG. 4A, the RLC layer 412 may deliver, to at least one layer higher than the RLC layer 412 (e.g., the application layer 420) , data associated with the received RLC PDUs 440a, 440c (e.g., when the second RLC PDU 440b is missing or absent) .

FIG. 12 illustrates an aspect of operation 504, at which at least one layer of the UE is configured to operate in the low-latency mode. In an aspect, operation 504 may include operation 1202 and operation 1204.

At operation 1202, the UE may receive, on a PHICH, at least one HARQ NACK message based on at least one transmission of a TB including a first RLC PDU having a first SN and first information. For example, the UE may send, in a MAC TB, a first RLC PDU, which may include a first SN and first information. Based on the MAC TB, the UE may receive at least one HARQ NACK message from the network, for example, when the MAC TB is unreceived. In the context of FIG. 4A, the MAC layer 410 may receive, on a PHICH, at least one HARQ NACK message 446 based on at least one transmission of a TB including a first RLC PDU 442a, which may include a first SN and first information.

At operation 1204, the UE may send, based on the at lcast one HARQ NACK message, a second RLC PDU including the first SN and second information. In an aspect, the second information may be smaller in size than the first information. For example, the UE may generate a new RLC PDU having second information smaller in size than the first information but having the first SN. The UE may send the new RLC PDU in a MAC TB. In the context of FIG. 4A, the MAC layer 410 may send, based on the at least one HARQ NACK message 446, a TB including a second RLC PDU (e.g., RLC PDU 442b) including the first SN and second information, the second information being smaller in size than the first information.

FIG. 13 illustrates an aspect of operation 504, at which at least one layer of the UE is configured to operate in the low-latency mode. In an aspect, operation 504 may include operation 1302 and operation 1304.

At operation 1302, the UE may configure a PDCP discard timer from a first duration to a second duration. The second duration may be shorter than the first duration. In an aspect, the first duration is configured by the network. For example, the UE may receive the first duration from a base station and configure the PDCP discard timer with the first duration. When the UE is to be configured in the low-latency mode, the UE may configure the PDCP discard timer from the first duration to the second duration. In the context of FIG. 4A, the PDCP layer 414 may configure an PDCP discard timer from a first duration to a second duration, and the second duration may be shorter than the first, and the first duration may be configured by the base station 460.

At operation 1304, the UE may discard at least one PDCP PDU based on expiration of the PDCP discard timer configured with the second duration. For example, the UE may detect expiration of the PDCP discard timer and may determine that the at least one PDCP PDU has not yet been sent. Therefore, the UE may discard the at least one PDPCP PDU. In the context of FIG. 4A, the PDCP layer 414 may discard at least one PDCP PDU based on expiration of a PDCP discard timer configured with the second duration.

FIG. 14 illustrates an aspect of operation 504, at which at least one layer of the UE is configured to operate in the low-latency mode. In an aspect, operation 504 may include operation 1402, operation 1404, operation 1406, and operation 1408.

At operation 1402, the UE may determine that at least one HARQ NACK message is transmitted from a first HARQ process based on an unreceived MAC TB associated with a first RLC PDU, the first RLC PDU being associated with a first SN. For example, the UE may determine that an RLC PDU is missing or absent (e.g., unreceived or due to decoding failure) . The UE may determine that a HARQ NACK message should be sent from the first HARQ process on which the MAC TB associated with first RLC PDU should have been received. The UE may transmit the HARQ NACK message on the first HARQ process. In the context of FIG. 4A, the UE may determine that at least one HARQ NACK message 444 is transmitted from a first HARQ process 430a based on an unreceived MAC TB associated with a first RLC PDU 440a, the first RLC PDU 440a associated with a first SN.

At operation 1404, the UE may determine that at least one first HARQ ACK message is transmitted from a second HARQ process based on a received MAC TB associated with the second RLC PDU, the second RLC PDU associated with a second SN higher than the first SN. For example, the UE may successfully receive the second RLC PDU, included in the MAC TB. The UE may send, in response to the successful reception, a HARQ ACK message. In the context of FIG. 4A, the MAC layer 410 may determine that at least one HARQ ACK message 450 is transmitted from a second HARQ process 430b based on a received MAC TB associated with a second RLC PDU 440b, the second RLC PDU 440b associated with a second SN higher than the first SN of the first RLC PDU 440a.

At operation 1406, the UE may send, based on the determination that the first HARQ ACK message is transmitted, a second HARQ ACK message instead of a HARQ NACK message. The second HARQ ACK message may be associated with the unreceived MAC TB associated with the first RLC PDU. For example, the UE may determine that, because later PDUs with higher SNs are successfully received, at least one earlier PDU that is unsuccessfully received should be acknowledged (e.g., because the earlier PDU is now stale) . Therefore, the UE may cause at least one ACK message to be transmitted for the at least one earlier PDU. In the context of FIG. 4A, the MAC layer may send, based on the determination that the first HARQ ACK message 450 is transmitted, a second HARQ ACK message 450 instead of a HARQ NACK message 444, the second HARQ ACK message 450 associated with the unreceived MAC TB associated with an unreceived first RLC PDU 440a.

At operation 1408, the UE may deliver, to at least one layer higher than the RLC layer without waiting for recording, the second RLC PDU associated with the second SN. For example, the UE may extract data from one or more RLC PDUs having SNs higher than the first SN and the UE may pass the extracted data up the radio protocol stack to the application layer. In the context of FIG. 4A, the RLC layer 412 may deliver, to at least one layer higher than the RLC layer 412 (e.g., the application layer 420) , data associated with the received

RLC PDUs

440b, 440c (e.g., when the first RLC PDU 440a is missing or absent) .

FIG. 15 illustrates an aspect of operation 504, at which at least one layer of the UE is configured to operate in the low-latency mode. In an aspect, operation 504 may include operation 1502 and operation 1504.

At operation 1502, the UE may configure a timer associated with a PHR from a first duration to a second duration. The second duration may be shorter than the first duration. In an aspect, the first duration is configured by the network. For example, the UE may receive the first duration from a base station and configure the timer associated with a PHR with the first duration. When the UE is to be configured in the low-latency mode, the UE may configure the timer associated with a PHR from the first duration to the second duration. In the context of FIG. 4A, the MAC layer 410 may configure a timer associated with a PHR from a first duration to a second duration, and the second duration may be shorter than the first duration, and the first duration may be configured by the base station 460.

At operation 1504, the UE may send a report indicating an amount of transmission power available to be used by the UE (e.g., a PHR) to the network based on expiration of the timer associated with a PHR configured with the second duration. For example, the UE may begin the timer associated with a PHR. Based on expiration of the timer associated with a PHR, the UE may send the report. In the context of FIG. 4A, the MAC layer 410 may send a PHR to the base station 460 based on expiration of the timer associated with a PHR configured with the second duration.

FIG. 16 illustrates an aspect of operation 504, at which at least one layer of the UE is configured to operate in the low-latency mode. In an aspect, operation 504 may include operation 1602 and operation 1604.

At operation 1602, the UE may configure a threshold associated with a PHR from a first value to a second value. The second value may be less than the first value. In an aspect, the first value is configured by the network. For example, the UE may receive the first value from a base station and configure the threshold associated with a PHR with the first value. When the UE is to be configured in the low-latency mode, the UE may configure the threshold associated with a PHR from the first value to the second value. In the context of FIG. 4A, the MAC layer 410 may configure a threshold associated with a PHR from a first value to a second value, and the second value may be less than the first, and the first value may be configured by the base station 460.

At operation 1604, the UE may send a report indicating an amount of transmission power available to be used by the UE (e.g., a PHR) to the network based on a measured path loss value that satisfies the threshold configured with the second value. For example, the UE may measure a path loss value that meets or exceeds the threshold. Based on the measured path loss value, the UE may send the report. In the context of FIG. 4A, the MAC layer 410 may send a PHR to the base station 460 based on a measured path loss value that satisfies the threshold configured with the second value.

FIG. 17 illustrates an aspect of operation 504, at which at least one layer of the UE is configured to operate in the low-latency mode. In an aspect, operation 504 may include operation 1702 and operation 1704.

At operation 1702, the UE may configure a transmit power from a first value to a second value. The second value may be greater than the first value. In an aspect, the first value is controlled by the network. For example, the UE may receive the first value from a base station and configure the transmit power with the first value. When the UE is to be configured in the low-latency mode, the UE may configure the transmit power from the first value to the second value. In the context of FIG. 4A, the PHY layer 406 may configure a transmit power from a first value to a second value, and the second value may be greater than the first value, and the first value may be configured by the base station 460.

At operation 1704, the UE may send signals to the network based on the transmit power configured with the second value. For example, the UE may adjust a transmit power to approximately match the second value. The UE may transmit signals to the network at the adjusted transmit power. In the context of FIG. 4A, the PHY layer 406 may transmit signals to the base station 460 at a transmit power configured with the second value.

FIG. 18 illustrates an aspect of operation 504, at which at least one layer of the UE is configured to operate in the low-latency mode. In an aspect, operation 504 may include operation 1802 and operation 1804.

At operation 1802, the UE may configure an SR retransmission timer from a first duration to a second duration. The second duration may be shorter than the first duration. In an aspect, the first duration is controlled by the network. For example, the UE may receive the first duration from a base station and configure the SR retransmission timer with the first duration. When the UE is to be configured in the low-latency mode, the UE may configure the SR retransmission timer from the first duration to the second duration. In the context of FIG. 4A, the MAC layer 410 may configure an SR retransmission timer from a first duration to a second duration, and the second duration may be shorter than the first duration, and the first duration may be controlled by the base station 460.

At operation 1804, the UE may send a SR based on expiration of the SR retransmission timer configured with the second duration. For example, the UE may begin the SR retransmission timer and may detect that an uplink grant is unreceived in response to the SR at expiration of the SR retransmission timer. Based on expiration of the SR retransmission timer, the UE may retransmit the SR. In the context of FIG. 4A, the MAC layer 410 may send an SR to the base station 460 based on expiration of the SR retransmission timer configured with the second duration.

FIG. 19 illustrates an aspect of operation 504, at which at least one layer of the UE is configured to operate in the low-latency mode. In an aspect, operation 504 may include operation 1902 and operation 1904.

At operation 1902, the UE may configure a threshold associated with a number of failed transmission attempts for an SR from a first value to a second value. The second value may be greater than the first value. In an aspect, the first value is configured by the network. For example, the UE may receive the first value from a base station and configure the threshold associated with a number of failed transmission attempts for an SR with the first value. When the UE is to be configured in the low-latency mode, the UE may configure the threshold associated with a number of failed transmission attempts for an SR from the first value to the second value. In the context of FIG. 4A, the MAC layer 410 may configure a threshold associated with a number of failed transmission attempts for an SR from a first value to a second value, and the second value may be greater than the first value, and the first value may be configured by the base station 460.

At operation 1904, the UE may release at least one resource associated with the SR on a PUCCH when the number of failed transmission attempts for the SR satisfies the threshold configured with the second value. For example, the UE may determine that the number of failed transmission attempts for the SR meets or exceeds the threshold. Based on the number of failed transmission attempts for the SR, the UE may release at least one resource associated with the SR on a PUCCH. In the context of FIG. 4A, the MAC layer 410 may release at least one resource associated with the SR on a PUCCH when the number of failed transmission attempts for the SR meets or exceeds threshold.

FIG. 20 illustrates an aspect of operation 504, at which at least one layer of the UE is configured to operate in the low-latency mode. In an aspect, operation 504 may include operation 2002, operation 2004, operation 2006, operation 2008, and/or operation 2010.

At operation 2002, the UE send, to a base station, a first RLC PDU having a first SN. In the context of FIG. 4A, the RLC layer 412 of the UE 402 may send, to the base station 460, a first RLC PDU 442a having a first SN.

At operation 2004, the UE may begin a timer based on the sending of the first RLC PDU. In an aspect, a duration of the timer may be based on a delay budget associated with continuous operation in a low-latency mode by the UE. The duration of the timer may be dynamically set. In the context of FIG. 4A, the RLC layer 412 may begin a timer based on the sending of the first RLC PDU 442a.

At operation 2006, the UE may send, to the base station after the first RLC PDU, at least one additional RLC PDU having a second SN higher than the first SN. In one aspect, the UE may set a polling bit of the first RLC PDU, e.g., to elicit status information from the base station that indicates RLC PDUs received by the base station. In the context of FIG. 4A, the RLC layer 412 may send, to the base station 460 after sending the first RLC PDU 442a, the other PDUs 442b-c having respective second and third SNs that are higher than the first SN.

At operation 2008, the UE may send, to the base station after expiry of the timer, a second RLC PDU having the first SN when ACK/NACK feedback is unreceived in association with the first RLC PDU having the first SN. In the context of FIG. 4A, the RLC layer 412 may resend the first RLC PDU 442a having the first SN when neither an ACK message 448 nor a NACK message 446 is received from the base station 460 for the first RLC PDU 442a.

At operation 2010, the UE may send, to the base station after expiry of the timer, a third RLC PDU having the second SN when ACK/NACK feedback is unreceived in association with the at least one additional RLC PDU having the second SN. In some aspects, the UE may set a respective polling bit in at least one of the other RLC PDUs 442b-c, e.g., to elicit status information from the base station that indicates RLC PDUs received by the base station. In the context of FIG. 4, the RLC layer 412 may resend the other RLC PDUs 442b-c having respective second and third SNs when neither ACK messages 448 nor NACK messages 446 are received from the base station 460 for the other RLC PDUs 442b-c.

FIG. 21 illustrates an aspect of operation 504, at which at least one layer of the UE is configured to operate in the low-latency mode. In an aspect, operation 504 may include operation 2102 and/or operation 2104.

At operation 2102, the UE may configure a threshold associated with a number of failed transmissions attempted for a SR from a first value to a second value. In an aspect, the first value may be controlled by a base station and the second value may be less than the first value. In an aspect, the configuration of the threshold associated with a number of failed transmissions attempted for the SR from the first value to the second value is based on the delay budget associated with continuous service during the low-latency mode. For example, the second value may be based on a delay budget associated with continuous service during the low-latency mode. In the context of FIG. 4B, the UE 402 may configure an SR retransmission threshold for attempting an SR 403 from a first value (e.g., controlled by the base station 460) to a second value that is lower than the first value.

At operation 2104, the UE may perform a RACH procedure with the base station to obtain an uplink grant when the number of failed transmissions attempted for the SR satisfies the threshold configured with the second value. For example, the UE may determine that a threshold number of SR attempts have failed (e.g., the UE has failed to obtain an uplink grant based on SR transmission) . Therefore, the UE may perform a RACH procedure and may obtain the uplink grant in the MSG4 of the RACH procedure. In some aspects, the UE may retain a PUCCH-SR configuration allocated by the base station. For example, the UE may refrain from releasing at least one PUCCH-SR resource allocated by the base station. In the context of FIG. 4B, the UE 402 may perform the RACH procedure 415 to obtain the uplink grant in the MSG4 411 when the number of failed transmissions attempted for the SRs 403a-n satisfies the threshold configured with the second value.

FIG. 22 is a conceptual data flow diagram 2200 illustrating the data flow between different means/components in an exemplary apparatus 2202. The apparatus 2202 may be a UE (e.g., the UE 104, the UE 350, the UE 402) . The apparatus 2202 depicts exemplary connections and/or data between different modules/means/components. One of ordinary skill will appreciate that such connections and/or data flow are to be regarded in as illustrative and, therefore, different and/or additional connections and/or data flow may be present in different aspects.

The apparatus 2202 may include a reception component 2204. The reception component 2204 may receive signals from a network (e.g., the network 2250) . The apparatus 2202 may further include a transmission component 2206. The transmission component 2206 may be configured to transmit signals to a network (e.g., the network 2250) .

The apparatus 2202 may include an application component 2212. The application component 2212 may include, for example, an application layer. In an aspect, the application component 2212 may include at least one application configured for real-time operation (e.g., the at least one application may be delay-sensitive) .

In one aspect, the application component 2212 may be configured to switch between a low-latency mode and a normal mode (e.g., conventional operation) . In one aspect, the application component 2212 may determine that the apparatus 2202 is to operate in a low-latency mode, for example, in association with real-time operation by the at least one application.

The application component 2212 may indicate, to the latency component 2210, that the apparatus 2202 is to operate in a low-latency mode. For example, the application component 2212 may inform the latency component 2210 through a QMI interface that the apparatus 2202 (e.g., the at least one application) is to communicate delay-sensitive traffic and, therefore, the apparatus 2202 is operate in the low-latency mode.

Further, the application component 2212 may indicate, to the latency component 2210, that the apparatus 2202 is to operate in the normal mode. For example, the application component 2212 may inform the latency component 2210 through the QMI interface that the apparatus 2202 (e.g., the at least one application) is no longer communicating delay-sensitive traffic and, therefore, the apparatus 2202 is to resume operation in the normal mode.

The apparatus 2202 may include a latency component 2210. The latency component 2210 may be included in the AS layer. In an aspect, the latency component 2210 may include or may be communicatively coupled with at least one layer of a radio protocol stack, such as a PHY layer (e.g., including a modem of the apparatus 2202) .

The latency component 2210 may determine that the apparatus 2202 is operate in the low-latency mode. In one aspect, the latency component 2210 may detect at least one of a transport protocol associated with traffic of the application component 2212 (e.g., UDP) , a network address associated with traffic of the application component 2212 (e.g., a network address of a server associated with real-time operation, such as an online gaming server or a VoIP server) , and/or a destination port associated with traffic of the application component 2212 (e.g., a UDP port) . Based on the detected at least one of the transport protocol, the network address, and/or the destination port, the latency component 2210 may determine that the apparatus 2202 is to operate in the low-latency mode.

In one aspect, the latency component 2210 may determine that the apparatus 2202 is to operate in the normal mode. For example, the latency component 2210 may detect that the application component 2212 is no longer communicating according to the at least one of the transport protocol, no longer communicating with the network address, and/or no longer communicating through the destination port. Accordingly, the latency component 2210 may cause the apparatus 2202 to resume operation in the normal mode instead of the low-latency mode.

The latency component 2210 may indicate, to the protocol stack component 2208, that the apparatus 2202 is to operate in the low-latency mode or in the normal mode. When the latency component 2210 indicates, to the protocol stack component 2208, that the apparatus 2202 is to operate in the low-latency mode, the protocol stack component 2208 may configure at least one layer of the apparatus 2202 to operate in the low-latency mode. The protocol stack component 2208 may then communicate with the network 2250 through the configured at least one layer.

The protocol stack component 2208 may include or may be communicatively coupled with at least a portion of a radio protocol stack, such as an L1 layer, L2 layer, and/or L3 layer. For example, the protocol stack component 2208 may include or may be communicatively coupled with at least a PHY layer, a MAC layer, an RLC layer, a PDCP layer, and/or an RRC layer (other layers may be included) .

The protocol stack component 2208 may configure the at least one layer of the apparatus 2202 to operate in the low-latency mode according to a plurality of aspects. In one aspect, the at least one layer may include the MAC layer. The protocol stack component 2208 may configure the at least one layer of the apparatus 2202 to operate in the low-latency mode by configuring a BSR retransmission timer from a first duration to a second duration. The first duration may be configured in the apparatus 2202 via RRC signaling. The second duration may be less than the first duration. The protocol stack component 2208 may send a BSR based on expiration of the BSR retransmission timer configured with the second duration.

In one aspect, the at least one layer may include the MAC layer. The protocol stack component 2208 may configure the at least one layer of the apparatus 2202 to operate in the low-latency mode by comparing, to a predetermined threshold, a number n of HARQ NACK messages received based on n transmissions of a TB including a BSR from a first HARQ process. The protocol stack component 2208 may send, on a second HARQ process, a BSR in a new TB based on comparison of the number n of HARQ NACK messages to the predetermined threshold.

In one aspect, the at least one layer may include the RLC layer and/or the MAC layer. The protocol stack component 2208 may configure the at least one layer of the apparatus 2202 to operate in the low-latency mode by comparing, to a predetermined threshold, a number x of HARQ NACK messages received on a PHICH based on x transmissions of a MAC TB including a first RLC PDU from a first HARQ process. The protocol stack component 2208 may retransmit the first RLC PDU based on comparison of the number x of HARQ NACK messages to the predetermined threshold (e.g., on the first HARQ process or on a second HARQ process) .

In one aspect, the at least one layer may include the RLC layer. The protocol stack component 2208 may configure the at least one layer of the apparatus 2202 to operate in the low-latency mode by configuring an RLC poll retransmission timer from a first duration to a second duration. The first duration may be configured in the apparatus 2202 via RRC signaling. The second duration may be less than the first duration. The protocol stack component 2208 may send a request for a status report from the network 2250 based on expiration of the RLC poll retransmission timer configured with the second duration. In an aspect, the status report may be associated with advancement of an AM window of the RLC layer.

In one aspect, the at least one layer may include the RLC layer. The protocol stack component 2208 may configure the at least one layer of the apparatus 2202 to operate in the low-latency mode by configuring an RLC transmission reordering timer from a first duration to a second duration. The first duration may be configured in the apparatus 2202 by the network 2250. The second duration may be less than the first duration. The protocol stack component 2208 may send a status report to the network 2250 based on expiration of the RLC transmission reordering timer configured with the second duration. In an aspect, the status report may indicate one or more SNs associated with one or more unreceived (or unacknowledged) RLC PDUs.

In one aspect, the at least one layer may include the RLC layer. The protocol stack component 2208 may configure the at least one layer of the apparatus 2202 to operate in the low-latency mode by determining that at least one expected RLC PDU is absent (e.g., unreceived and/or unacknowledged) . The protocol stack component 2208 may send, based on the determination that the at least one expected RLC PDU is absent, an ACK message instead of a NACK message when an SN of a most recently received RLC PDU corresponds to a highest expected SN (e.g., a VR_H value) . The protocol stack component 2208 may deliver, to at least one layer higher than the RLC layer, data associated with one or more RLC PDUs, the one or more RLC PDUs including the most recently received RLC PDU and having a respective SN higher than the SN of the at least one expected RLC PDU.

In one aspect, the at least one layer may include the RLC layer and/or the MAC layer. The protocol stack component 2208 may configure the at least one layer of the apparatus 2202 to operate in the low-latency mode by receiving, on a PHICH, at least one HARQ NACK message based on at least one transmission of a TB including a first RLC PDU. The first RLC PDU may include a first SN and first information. The protocol stack component 2208 may send, based on the at least one HARQ NACK message, a second RLC PDU. The second RLC PDU may include the first SN (i.e., the same SN as the first RLC PDU) and may include second information. The second information may be smaller in size than the first information.

In one aspect, the at least one layer may include the PDCP layer. The protocol stack component 2208 may configure the at least one layer of the apparatus 2202 to operate in the low-latency mode by configuring a PDCP discard timer from a first duration to a second duration. The first duration may be configured in the apparatus 2202 by the network 2250. The second duration may be less than the first duration. The protocol stack component 2208 may discard at least one PDCP PDU based on expiration of the PDCP timer configured with the second duration.

In one aspect, the at least one layer may include the RLC layer and/or the MAC layer. The protocol stack component 2208 may configure the at least one layer of the apparatus 2202 to operate in the low-latency mode by determining that at least one HARQ NACK message is transmitted from a first HARQ process based on an unreceived MAC TB associated with a first RLC PDU. The first RLC PDU may be associated with a first SN. The protocol stack component 2208 may determine that at least one first HARQ ACK message is transmitted from a second HARQ process based on a received MAC TB associated with a second RLC PDU. The second RLC PDU may be associated with a second SN higher than the first SN. The protocol stack component 2208 may send, based on the determination that the first HARQ ACK message is transmitted, a second HARQ ACK message instead of a HARQ NACK message. The second HARQ ACK message may be associated with the unreceived MAC TB associated with the first RLC PDU. The protocol stack component 2208 may deliver, to at least one layer higher than the RLC layer and without waiting for reordering, the second RLC PDU associated with the second SN.

In one aspect, the at least one layer may include the MAC layer. The protocol stack component 2208 may configure the at least one layer of the apparatus 2202 to operate in the low-latency mode by configuring a timer associated with a PHR (e.g., a periodic PHR timer and/or a PHR prohibit timer) from a first duration to a second duration. The first duration may be configured in the apparatus 2202 by the network 2250. The second duration may be less than the first duration. The protocol stack component 2208 may send a report indicating an amount of transmission power available to be used by the apparatus 2202 (e.g., a PHR) based on expiration of the timer associated with the PHR that is configured with the second duration.

In one aspect, the at least one layer may include the MAC layer. The protocol stack component 2208 may configure the at least one layer of the apparatus 2202 to operate in the low-latency mode by configuring a threshold associated with a PHR from a first value to a second value. The first value may be configured by the network 2250 in the apparatus 2202. The second value may be less than the first value. The protocol stack component 2208 may send, based on a measured path loss value that satisfies the threshold configured with the second value, a PHR.

In one aspect, the at least one layer may include the PHY layer. The protocol stack component 2208 may configure the at least one layer of the apparatus 2202 to operate in the low-latency mode by configuring a transmit power from a first value to a second value. The first value may be controlled in the apparatus 2202 by the network 2250. The second value may be greater than the first value. The protocol stack component 2208 may transmit, based on the transmit power configured with the second value, signals to the network 2250.

In one aspect, the at least one layer may include the MAC layer. The protocol stack component 2208 may configure the at least one layer of the apparatus 2202 to operate in the low-latency mode by configuring a retransmission timer associated with an SR from a first duration to a second duration. The first duration may be controlled in the apparatus 2202 by the network 2250. The second duration may be less than the first duration. The retransmission timer associated with the SR may be an sr-ProhibitTimer, which may be a timer for SR transmission on a PUCCH (e.g., as defined by a 3GPP technical specification 36.321 and/or 36.213) . The protocol stack component 2208 may resend an SR based on expiration of the retransmission timer associated with the PHR that is configured with the second duration.

In one aspect, the at least one layer may include the PHY layer and/or the MAC layer. The protocol stack component 2208 may configure the at least one layer of the apparatus 2202 to operate in the low-latency mode by configuring a threshold associated with a number of failed transmissions attempted for an SR from a first value to a second value. The first value may be controlled by the network 2250 in the apparatus 2202. The second value may be greater than the first value. The protocol stack component 2208 may release at least one resource associated with the SR on a PUCCH when the number of failed transmissions attempted for the SR satisfies the threshold configured with the second value.

In one aspect, the at least one layer may include the RLC layer. The protocol stack component 2208 may configure the at least one layer of the apparatus 2202 to operate in the low-latency mode by sending, to the network 2250, a first RLC PDU having a first SN and by beginning a timer based on the sending of the first RLC PDU. The protocol stack component 2208 may further send one or more RLC PDUs each having a respective SN higher than the first SN after beginning the timer. In one aspect, the timer may have a duration that is configured by the protocol stack component 2208 based on a delay budget. If ACK/NACK feedback for the first RLC PDU having the first SN is unreceived at expiry of the timer, the protocol stack component 2208 may resend the first RLC PDU (e.g., a second RLC PDU having the first SN, which may include the same content as the first RLC PDU) to the network 2250. In an aspect, the protocol stack componeut 2208 may set a polling bit of the second RLC PDU to elicit status information from the network 2250. In an aspect, the protocol stack component 2208 may resend, to the network 2250, the one or more of the other RLC PDUs having respective SNs higher than the first SN at the expiry of the timer when ACK/NACK feedback is also unreceived for the one or more other RLC PDUs.

In one aspect, the at least one layer may include the MAC layer and/or PHY layer. The protocol stack component 2208 may configure the at least one layer of the apparatus 2202 to operate in the low-latency mode by configuring a threshold associated with a number of failed transmissions attempted for an SR from a first value to a second value. In an aspect, the first value may be controlled by the network 2250 and the second value may be less than the first value. In an aspect, the configuration of the threshold associated with the number of failed transmissions attempted for the SR from the first value to the second value may be based on a delay budget associated with continuous service during the low-latency mode. The protocol stack component 2208 may attempt to elicit an uplink grant by sending one or more SRs. If the number of transmitted SRs satisfies the threshold configured with the second value and the apparatus 2202 has not received an uplink grant, the protocol stack component 2208 may perform a RACH procedure with the network 2250 to obtain an uplink grant (e.g., in a MSG4 of a RACH procedure) . In one aspect, the means for configuring the at least one layer of the wireless communications device to operate in the low-latency mode is configured to refrain from releasing one or more resources of a PUCCH allocated for SR transmission.

The apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowcharts of FIGs. 5-21. As such, each block in the aforementioned flowcharts of FIGs. 5-21 may be performed by a component and the apparatus may include one or more of those components. The components may be one or more hardware components specifically configured to carry out the stated processes/algorithm, implemented by a processor configured to perform the stated processes/algorithm, stored within a computer-readable medium for implementation by a processor, or some combination thereof.

FIG. 23 is a diagram 2300 illustrating an example of a hardware implementation for an apparatus 2202′employing a processing system 2314. The processing system 2314 may be implemented with a bus architecture, represented generally by the bus 2324. The bus 2324 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 2314 and the overall design constraints. The bus 2324 links together various circuits including one or more processors and/or hardware components, represented by the processor 2304, the

components

2204, 2206, 2208, 2210, 2212 and the computer-readable medium /memory 2306. The bus 2324 may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further.

The processing system 2314 may be coupled to a transceiver 2310. The transceiver 2310 is coupled to one or more antennas 2320. The transceiver 2310 provides a means for communicating with various other apparatus over a transmission medium. The transceiver 2310 receives a signal from the one or more antennas 2320, extracts information from the received signal, and provides the extracted information to the processing system 2314, specifically the reception component 2204. In addition, the transceiver 2310 receives information from the processing system 2314, specifically the transmission component 2206, and based on the received information, generates a signal to be applied to the one or more antennas 2320. The processing system 2314 includes a processor 2304 coupled to a computer-readable medium /memory 2306. The processor 2304 is responsible for general processing, including the execution of software stored on the computer-readable medium /memory 2306. The software, when executed by the processor 2304, causes the processing system 2314 to perform the various functions described supra for any particular apparatus. The computer-readable medium /memory 2306 may also be used for storing data that is manipulated by the processor 2304 when executing software. The processing system 2314 further includes at least one of the

components

2204, 2206, 2208, 2210, 2212. The components may be software components running in the processor 2304, resident/stored in the computer readable medium /memory 2306, one or more hardware components coupled to the processor 2304, or some combination thereof. The processing system 2314 may be a component of the UE 350 and may include the memory 360 and/or at least one of the TX processor 368, the RX processor 356, and the controller/processor 359.

In one configuration, the apparatus 2202/2202′for wireless communication includes means for determining that the apparatus 2202/2202’is to operate in a low-latency mode. The apparatus 2202/2202′may further include means for configuring at least one layer of the apparatus 2202/2202’to operate in the low-latency mode based on the determination that the apparatus 2202/2202’is to operate in the low-latency mode. The apparatus 2202/2202′may include means for communicating with a network through the configured at least one layer.

In an aspect, the at least one layer includes an RLC layer, and the means for configuring the at least one layer of the wireless communications device to operate in the low-latency mode is configured to send, to a base station, a first RLC PDU having a first SN, begin a timer based on the sending of the first RLC PDU, and send, to the base station based on expiry of the timer, a second RLC PDU having the first SN when ACK/NACK feedback is unreceived in association with the first RLC PDU having the first SN. In an aspect, the second RLC PDU having the first SN includes a polling bit set to elicit status information from the base station that indicates RLC PDUs received by the base station. In an aspect, the means for configuring the at least one layer of the wireless communications device to operate in the low-latency mode is further configured to send, to the base station after the first RLC PDU, at least one additional RLC PDU having a second SN higher than the first SN, and send, to the base station based on the expiry of the timer, a third PDU having the second SN when ACK/NACK feedback is unreceived in association with the at least one additional PDU having the second SN. In an aspect, a duration of the timer is based on a delay budget associated with continuous service during the low-latency mode.

In an aspect, the at least one layer comprises a media access control (MAC) layer, and the means for configuring the at least one layer of the wireless communications device to operate in the low-latency mode is configured to configure a threshold associated with a number of failed transmissions attempted for a SR from a first value to a second value, the first value being controlled by a base station and the second value being less than the first value, and perform a RACH procedure with the base station to obtain an uplink grant when the nmnber of failed transmissions attempted for the SR satisfies the threshold configured with the second value. In an aspect, the configuration of the threshold associated with the number of failed transmissions attempted for the SR from the first value to the second value is based on a delay budget associated with continuous service during the low-latency mode.

The aforementioned means may be one or more of the aforementioned components of the apparatus 2202 and/or the processing system 2314 of the apparatus 2202′configured to perform the functions recited by the aforementioned means. As described supra, the processing system 2314 may include the TX Processor 368, the RX Processor 356, and the controller/processor 359. As such, in one configuration, the aforementioned means may be the TX Processor 368, the RX Processor 356, and the controller/processor 359 configured to perform the functions recited by the aforementioned means.

It is understood that the specific order or hierarehy of blocks in the processes /flowcharts disclosed is an illustration of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of blocks in the processes /flowcharts may be rearranged. Further, some blocks may be combined or omitted. The accompanying method claims present elements of the various blocks in a sample order, and are not meant to be limited to the specific order or hierarchy presented.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more. ” The word “exemplary” is used herein to mean “serving as an example, instance, or illustration. ” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects. Unless specifically 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 “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 “A, B, C, or any combination thereof” may be A only, B only, C only, A andB, A and C, B and C, or A and B and C, where any such combinations may contain one or more member or members of A, B, or C. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art 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 regardless of whether such disclosure is explicitly recited in the claims. The words “module, ” “mechanism, ” “element, ” “device, ” and the like may not be a substitute for the word “means. ” As such, no claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for. ”

Claims

A method of wireless communication for a wireless communications device, the method comprising:

determining that the wireless communications device is to operate in a low-latency mode;

configuring at least one layer of the wireless communications device to operate in the low-latency mode based on the determination that the wireless communications device is to operate in the low-latency mode; and

communicating with a network through the configured at least one layer.
The method of claim l, wherein the at least one layer includes a radio link control layer (RLC) layer, and the configuring the at least one layer of the wireless communications device to operate in the low-latency mode comprises:

sending, to a base station, a first RLC protocol data unit (PDU) having a first sequence number (SN) ; and

beginning a timer based on the sending of the first RLC PDU; and

sending, to the base station based on expiry of the timer, a second RLC PDU having the first SN when acknowledgement (ACK) /negative acknowledgement (NACK) feedback is unreceived in association with the first RLC PDU having the first SN.
The method of claim 2, wherein the second RLC PDU having the first SN includes a polling bit set to elicit status information from the base station that indicates RLC PDUs received by the base station.
The method of claim 2, further comprising:

sending, to the base station after the first RLC PDU, at least one additional RLC PDU having a second SN higher than the first SN; and

sending, to the base station based on the expiry of the timer, a third PDU having the second SN when ACK/NACK feedback is unreceived in association with the at least one additional PDU having the second SN.
The method of claim 2, wherein a duration of the timer is based on a delay budget associated with continuous service during the low-latency mode.
The method of claim 1, wherein the at least one layer comprises a media access control (MAC) layer, and the configuring the at least one layer of the wireless communications device to operate in the low-latency mode comprises:

configuring a threshold associated with a number of failed transmissions attempted for a scheduling request (SR) from a first value to a second value, the first value being controlled by a base station and the second value being less than the first value; and

performing a random access channel (RACH) procedure with the base station to obtain an uplink grant when the number of failed transmissions attempted for the SR satisfies the threshold configured with the second value.
The method of claim 6, wherein the configuring the threshold associated with the number of failed transmissions attempted for the SR from the first value to the second value is based on a delay budget associated with continuous service during the low-latency mode.
The method of claim 6, wherein the configuring the at least one layer of the wireless communications device to operate in the low-latency mode further comprises:

refraining from releasing one or more resources of a physical uplink control channel (PUCCH) allocated for SR transmission.
A wireless communications device comprising:

means for determining that the wireless communications device is to operate in a low-latency mode;

means for configuring at least one layer of the wireless communications device to operate in the low-latency mode based on the determination that the wireless communications device is to operate in the low-latency mode; and

means for communicating with a network through the configured at least one layer.
The wireless communications device of claim 9, wherein the at least one layer includes a radio link control layer (RLC) layer, and the means for configuring the at least one layer of the wireless communications device to operate in the low-latency mode is configured to:

send, to a base station, a first RLC protocol data unit (PDU) having a first sequence number (SN) ; and

begin a timer based on the sending of the first RLC PDU; and

send, to the base station based on expiry of the timer, a second RLC PDU having the first SN when acknowledgement (ACK) /negative acknowledgement (NACK) feedback is unreceived in association with the first RLC PDU having the first SN.
The wireless communications device of claim 10, wherein the second RLC PDU having the first SN includes a polling bit set to elicit status information from the base station that indicates RLC PDUs received by the base station.
The wireless communications device of claim 10, wherein the means for configuring the at least one layer of the wireless communications device to operate in the low-latency mode is further configured to:

send, to the base station after the first RLC PDU, at least one additional RLC PDU having a second SN higher than the first SN; and

send, to the base station based on the expiry of the timer, a third PDU having the second SN when ACK/NACK feedback is unreceived in association with the at least one additional PDU having the second SN.
The wireless communications device of claim 10, wherein a duration of the timer is based on a delay budget associated with continuous service during the low-latency mode.
The wireless communications device of claim 10, wherein the at least one layer comprises a media access control (MAC) layer, and the means for configuring the at least one layer of the wireless communications device to operate in the low-latency mode is configured to:

configure a threshold associated with a number of failed transmissions attempted for a scheduling request (SR) from a first value to a second value, the first value being controlled by a base station and the second value being less than the first value; and

perform a random access channel (RACH) procedure with the base station to obtain an uplink grant when the number of failed transmissions attempted for the SR satisfies the threshold configured with the second value.
The wireless communications device of claim 14, wherein the configuration of the threshold associated with the number of failed transmissions attempted for the SR from the first value to the second value is based on a delay budget associated with continuous service during the low-latency mode.
The wireless communications device of claim 14, wherein the means for configuring the at least one layer of the wireless communications device to operate in the low-latency mode is configured to:

refrain from releasing one or more resources of a physical uplink control channel (PUCCH) allocated for SR transmission.
A wireless communications device comprising:

a memory; and

at least one processor coupled to the memory and configured to:

determine that the wireless communications device is to operate in a low-latency mode;

configure at least one layer of the wireless communications device to operate in the low-latency mode based on the determination that the wireless communications device is to operate in the low-latency mode; and

communicate with a network through the configured at least one layer.
The wireless communications device of claim 17, wherein the at least one layer includes a radio link control layer (RLC) layer, and the configuration of the at least one layer of the wireless communications device to operate in the low-latency mode comprises:

sending, to a base station, a first RLC protocol data unit (PDU) having a first sequence number (SN) ; and

beginning a timer based on the sending of the first RLC PDU; and sending, to the base station based on expiry of the timer, a second RLC PDU having the first SN when acknowledgement (ACK) /negative acknowledgement (NACK) feedback is unreceived in association with the first RLC PDU having the first SN.
The wireless communications device of claim 18, wherein the second RLC PDU having the first SN includes a polling bit set to elicit status information from the base station that indicates RLC PDUs received by the base station.
The wireless communications device of claim 18, wherein the at least one processor is further configured to:

send, to the base station after the first RLC PDU, at least one additional RLC PDU having a second SN higher than the first SN; and

send, to the base station based on the expiry of the timer, a third PDU having the second SN when ACK/NACK feedback is unreceived in association with the at least one additional PDU having the second SN.
The wireless communications device of claim 18, wherein a duration of the timer is based on a delay budget associated with continuous service during the low-latency mode.
The wireless communications device of claim 17, wherein the at least one layer comprises a media access control (MAC) layer, and the configuration of the at least one layer of the wireless communications device to operate in the low-latency mode comprises:

configuring a threshold associated with a number of failed transmissions attempted for a scheduling request (SR) from a first value to a second value, the first value being controlled by a base station and the second value being less than the first value; and

performing a random access channel (RACH) procedure with the base station to obtain an uplink grant when the number of failed transmissions attempted for the SR satisfies the threshold configured with the second value.
The wireless communications device of claim 22, wherein the configuration of the threshold associated with the number of failed transmissions attempted for the SR from the first value to the second value is based on a delay budget associated with continuous service during the low-latency mode.
The wireless communications device of claim 22, wherein the configuration of the at least one layer of the wireless communications device to operate in the low-latency mode further comprises:

refraining from releasing one or more resources of a physical uplink control channel (PUCCH) allocated for SR transmission.
A computer-readable medium storing computer-executable code for wireless communication by a wireless communications device, comprising code to:

determine that the wireless communications device is to operate in a low-latency mode;

configure at least one layer of the wireless communications device to operate in the low-latency mode based on the determination that the wireless communications device is to operate in the low-latency mode; and

communicate with a network through the configured at least one layer.