Method and apparatus for data transmission in RACH procedure

Abstract

The present disclosure relates to methods and apparatus for wireless communications, including devices, such as user equipment (UE) and / or base stations. In one aspect, the device may determine to enter a two-step RACH procedure in an RRC inactive state. The device may also determine to transmit uplink data in a payload of message A (MsgA) of the two-step RACH procedure. The device may also transmit the MsgA of the two-step RACH procedure, the MsgA including the payload, the payload including at least the uplink data. In addition, the device may monitor MsgB of the two-step RACH procedure. The device may also receive the MsgB of the two-step RACH procedure, wherein the MsgB includes a fallback indication, the fallback indication including a fallback RAR. In addition, the device may retransmit the payload of the MsgA upon receiving the MsgB including the fallback indication.

Description

Technical Field

[0001] The present disclosure relates generally to communication systems, and more particularly, to random access channel (RACH) procedures in wireless communication systems. Background Art

[0002] Wireless communication systems are widely deployed to provide a variety of telecommunication services, such as telephony, video, data, messaging, and broadcasting. 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.

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

[0004] 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 exhaustive overview of all contemplated aspects and is neither intended to identify important or critical elements of all aspects nor to delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

[0005] In one aspect of the present disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a user equipment (UE). The apparatus may receive an instruction from a base station to enter the RRC inactive state. The apparatus may also determine to enter a two-step random access channel (RACH) procedure in the radio resource control (RRC) inactive state. The apparatus may also determine to transmit uplink data in a payload of message A (MsgA) of the two-step RACH procedure. In addition, the apparatus may also transmit the MsgA of the two-step RACH procedure, the MsgA including the payload, the payload including at least the uplink data. The apparatus may also monitor message B (MsgB) of the two-step RACH procedure. The apparatus may also receive the MsgB of the two-step RACH procedure, wherein the MsgB includes a fallback indication, the fallback indication including a fallback random access response (RAR). In addition, the apparatus may retransmit the payload of the MsgA upon receiving the MsgB including the fallback indication. The apparatus may also, after receiving the MsgB including the fallback indication, transmit Message 3 (Msg3), wherein hybrid automatic repeat request (HARQ) retransmission is applied to the Msg3. The apparatus may also monitor Message 4 (Msg4) after transmitting the Msg3. In addition, the apparatus may receive the Msg4, wherein the Msg4 includes at least one of preconfigured uplink resources (PUR) or downlink data. The apparatus may also store the uplink data in at least one buffer, wherein the payload of the retransmitted MsgA or the retransmitted payload of the MsgA includes at least one of an RRC message or a data request message. The apparatus may also retransmit the MsgA when the MsgB or Msg4 is not received, the retransmitted MsgA including a payload and a preamble, wherein the retransmitted MsgA includes at least one of an RRC message or a data request message. The apparatus may also switch from the two-step RACH procedure to a four-step RACH procedure when the MsgA is retransmitted at least a configured threshold number of retransmissions. The apparatus may also select one or more preamble groups for the four-step RACH procedure, wherein a transport block (TB) size of each of the one or more preamble groups of the four-step RACH procedure is different from a TB size of each of the one or more preamble groups of the two-step RACH.

[0006] In another aspect of the present disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a base station. The apparatus may transmit an instruction to at least one user equipment (UE) to enter a radio resource control (RRC) inactive state. The apparatus may also receive message A (MsgA) of a two-step random access channel (RACH) procedure, the MsgA including a payload, the payload including at least uplink data. The apparatus may also receive the retransmitted payload of the MsgA when transmitting the MsgB including the fallback indication. In addition, the apparatus may transmit message B (MsgB) of the two-step RACH procedure. The apparatus may also receive message 3 (Msg3) after transmitting the MsgB including the fallback indication, wherein hybrid automatic repeat request (HARQ) retransmission is applied to the Msg3. The apparatus may also transmit message 4 (Msg4), wherein the Msg4 includes at least one of pre-configured uplink resources (PUR) or downlink data. The apparatus may also receive a retransmitted MsgA including a payload and a preamble, wherein the retransmitted MsgA includes at least one of an RRC message or a data request message.

[0007] To accomplish the foregoing and related ends, one or more aspects include the features fully described below and particularly pointed out in the claims. The following description and the accompanying drawings set forth in detail certain illustrative features of one or more aspects. However, these features are indicative of but a few of the various ways in which the principles of the various aspects may be employed, and this description is intended to include all such aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a diagram illustrating an example of a wireless communication system and an access network.

[0009] Figure 2A is a diagram illustrating an example of a first frame according to aspects of the present disclosure.

[0010] Figure 2B is a diagram illustrating an example of DL channels within a subframe according to aspects of the present disclosure.

[0011] Figure 2C is a diagram illustrating an example of a second frame according to aspects of the present disclosure.

[0012] Figure 2D is a diagram illustrating an example of UL channels within a subframe in accordance with aspects of the present disclosure.

[0013] Figure 3 is a diagram illustrating an example of a base station and a user equipment (UE) in an access network.

[0014] Figure 4 is a diagram illustrating exemplary communications between a UE and a base station in accordance with one or more techniques of this disclosure.

[0015] Figure 5 is a diagram illustrating exemplary communications between a UE and a base station in accordance with one or more techniques of this disclosure.

[0016] Figure 6 is a diagram illustrating exemplary communications between a UE and a base station in accordance with one or more techniques of this disclosure.

[0017] Figure 7 is a diagram illustrating exemplary communications between a UE and a base station in accordance with one or more techniques of this disclosure.

[0018] Figure 8 is a diagram illustrating exemplary communications between a UE and a base station in accordance with one or more techniques of this disclosure.

[0019] Figure 9 is a flow chart of a method of wireless communication.

[0020] Figure 10 is a flow chart of a method of wireless communication.

[0021] Figure 11 is a diagram showing an example of a hardware implementation for an exemplary apparatus.

[0022] Figure 12 is a diagram showing an example of a hardware implementation for an exemplary apparatus. DETAILED DESCRIPTION

[0023] The detailed description set forth below in conjunction with the accompanying drawings is intended as a description of various configurations and is not intended to represent the only configuration in which the concepts described herein may be practiced. The detailed description includes specific details to provide a comprehensive understanding of the various concepts. However, it will be apparent to one of ordinary skill 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 to avoid obscuring such concepts.

[0024] Several aspects of telecommunications systems will now be presented with reference to various apparatuses and methods. These apparatuses 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, "elements"). These elements may be implemented using electronic hardware, computer software, or a combination thereof. Whether such elements are implemented as hardware or software depends on the specific application and design constraints imposed on the overall system.

[0025] As an example, any part of an element or any combination of elements may be implemented as a "processing system" comprising 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, system-on-chip (SoCs), baseband processors, field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gating logic, discrete hardware circuits, and other suitable hardware configured to perform the various functions described throughout this disclosure. One or more processors in a processing system can execute software. Whether referred to as software, firmware, middleware, microcode, hardware description language, or other, software should be broadly interpreted as meaning instructions, instruction sets, codes, code segments, program codes, programs, subroutines, software components, applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, procedures, and / or functions, etc.

[0026] Therefore, in one or more exemplary embodiments, the functions described can be implemented in hardware, software, or any combination thereof. If implemented in software, the functions can be stored or encoded as one or more instructions or codes on a computer-readable medium. Computer-readable media include computer storage media. The storage medium can be any available medium that a computer can access. By way of example and not limitation, such computer-readable media may include random access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), optical disk storage devices, magnetic disk storage devices, other magnetic storage devices, a combination of the above-mentioned types of computer-readable media, or any other medium that can be used to store computer-executable code in the form of computer-accessible instructions or data structures.

[0027] Figure 1 1 is a diagram illustrating an example of a wireless communication system and access network 100. The wireless communication system (also referred to as a wireless wide area network (WWAN)) includes a base station 102, a UE 104, an evolved packet core (EPC) 160, and another core network 190 (e.g., a 5G core (5GC)). The base station 102 may include a macro cell (a high-power cellular base station) and / or a small cell (a low-power cellular base station). A macro cell includes a base station. A small cell includes a femto cell, a pico cell, and a micro cell.

[0028] A base station 102 configured for 4G LTE (collectively referred to as the Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)) may interface with the EPC 160 via a first backhaul link 132 (e.g., an S1 interface). A base station 102 configured for 5G NR (collectively referred to as the Next Generation RAN (NG-RAN)) may interface with the core network 190 via a second backhaul link 184. The base station 102 may perform one or more of the following functions, among other things: transmission of user data, radio channel encryption and decryption, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection establishment and release, load balancing, non-access stratum (NAS) message distribution, NAS node selection, synchronization, radio access network (RAN) sharing, multimedia broadcast multicast service (MBMS), subscriber and equipment tracking, RAN information management (RIM), paging, positioning, and delivery of warning messages. Base stations 102 can communicate with each other directly or indirectly (eg, through EPC 160 or core network 190) via a third backhaul link 134 (eg, an X2 interface). First backhaul link 132, second backhaul link 184, and third backhaul link 134 can be wired or wireless.

[0029] Base stations 102 can communicate wirelessly with UEs 104. Each of base stations 102 can provide communication coverage for a corresponding geographic coverage area 110. There can be overlapping geographic coverage areas 110. For example, a small cell 102′ can have a coverage area 110′ that overlaps with the coverage area 110 of one or more macro base stations 102. A network that includes both small cells and macro cells can be referred to as a heterogeneous network. A heterogeneous network can also include a home evolved Node B (eNB) (HeNB), which can provide service to a restricted group called a closed subscriber group (CSG). The communication link 120 between the base station 102 and the UE 104 can include uplink (UL) (also known as reverse link) transmissions from the UE 104 to the base station 102 and / or downlink (DL) (also known as forward link) transmissions from the base station 102 to the UE 104. The communication link 120 can use multiple-input multiple-output (MIMO) antenna technology, including spatial multiplexing, beamforming, and / or transmit diversity. The communication link can be carried out over one or more carriers. Base station 102 / UE 104 can use spectrum with a bandwidth of up to Y MHz (e.g., 5, 10, 15, 20, 100, 400 MHz, etc.) per carrier allocated in a carrier aggregation for transmission in each direction up to a total of Yx MHz (x component carriers). The carriers may or may not be adjacent to each other. The allocation of carriers may be asymmetric for DL ​​and UL (e.g., more or fewer carriers may be allocated for DL ​​than for UL). Component carriers may include a primary component carrier and one or more secondary component carriers. The primary component carrier may be referred to as a primary cell (PCell) and the secondary component carriers may be referred to as secondary cells (SCells).

[0030] Some UEs 104 may communicate with each other using device-to-device (D2D) communication links 158. The D2D communication links 158 may use the DL / UL WWAN spectrum. The D2D communication links 158 may use one or more sidelink channels, such as a physical sidelink broadcast channel (PSBCH), a physical sidelink discovery channel (PSDCH), a physical sidelink shared channel (PSSCH), and a physical sidelink control channel (PSCCH). D2D communication may be performed via various wireless D2D communication systems, such as, for example, WiMedia, Bluetooth, ZigBee, Wi-Fi based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, LTE, or NR.

[0031] The wireless communication system may also include a Wi-Fi access point (AP) 150 that communicates with a Wi-Fi station (STA) 152 via a communication link 154, for example, in a 5 GHz unlicensed spectrum. When communicating in an unlicensed frequency spectrum, the STA 152 / AP 150 may perform a clear channel assessment (CCA) prior to communication to determine whether the channel is available.

[0032] The small cell 102′ can operate in licensed and / or unlicensed frequency spectrum. When operating in the unlicensed frequency spectrum, the small cell 102′ can adopt NR and use the same unlicensed frequency spectrum (e.g., 5 GHz, etc.) used by the Wi-Fi AP 150. The small cell 102′ adopting NR in the unlicensed frequency spectrum can improve the coverage of the access network and / or increase the capacity of the access network.

[0033] The electromagnetic spectrum is often subdivided into various classes, bands, channels, etc. based on frequency / wavelength. In 5G NR, two initial operating bands have been identified with the frequency range names FR1 (410 MHz - 7.125 GHz) and FR2 (24.25 GHz - 52.6 GHz). Frequencies between FR1 and FR2 are often referred to as mid-band frequencies. Although a portion of FR1 is greater than 6 GHz, FR1 is often (interchangeably) referred to as the "sub-6 GHz" band in various documents and articles. A similar naming issue sometimes arises with respect to FR2, which is often (interchangeably) referred to as "millimeter wave" in documents and articles, although it is different from the extremely high frequency (EHF) band (30 GHz to 300 GHz) which is identified as a "millimeter wave" band by the International Telecommunication Union (ITU).

[0034] With the foregoing in mind, unless otherwise specifically stated, it should be understood that the term "sub-6 GHz" and the like (if used herein) can broadly refer to frequencies that may be lower than 6 GHz, may be within FR1, or may include mid-band frequencies. Furthermore, unless otherwise specifically stated, it should be understood that the term "millimeter wave" and the like (if used herein) can broadly refer to frequencies that may be lower than 6 GHz, may be within FR1, or may include mid-band frequencies. Furthermore, unless otherwise specifically stated, it should be understood that the term "millimeter wave" and the like (if used herein) can broadly refer to frequencies that may be mid-band frequencies, may be within FR2, or may be within the EHF band.

[0035] Base station 102, whether a small cell 102′ or a large cell (e.g., a macro base station), may include and / or be referred to as an eNB, a gNodeB (gNB), or another type of base station. Some base stations, such as gNB 180, may operate in the traditional sub-6 GHz spectrum, millimeter wave frequencies, and / or near millimeter wave frequencies for communicating with UE 104. When gNB 180 operates in millimeter wave or near millimeter wave frequencies, gNB 180 may be referred to as a millimeter wave base station. Millimeter wave base station 180 may utilize beamforming 182 with UE 104 to compensate for path loss and short range. Base station 180 and UE 104 may each include multiple antennas (such as antenna elements, antenna panels, and / or antenna arrays) to facilitate beamforming.

[0036] Base station 180 may transmit beamformed signals in one or more transmit directions 182′ to UE 104. UE 104 may receive beamformed signals from base station 180 in one or more receive directions 182″. UE 104 may also transmit beamformed signals in one or more transmit directions to base station 180. Base station 180 may receive beamformed signals in one or more receive directions from UE 104. Base station 180 / UE 104 may perform beam training to determine the best receive direction and transmit direction for each of base station 180 / UE 104. The transmit direction and receive direction of base station 180 may be the same or different. The transmit direction and receive direction of UE 104 may be the same or different.

[0037] 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 communicate with a Home Subscriber Server (HSS) 174. The MME 162 is a control node that handles signaling between the UE 104 and the EPC 160. Generally, the MME 162 provides bearer and connection management. All user Internet Protocol (IP) packets are transmitted through the Serving Gateway 166, which itself is connected to the PDN Gateway 172. The PDN Gateway 172 provides UE IP address allocation and other functions. The PDN Gateway 172 and the BM-SC 170 are connected to IP Services 176. IP Services 176 may include the Internet, an intranet, an IP Multimedia Subsystem (IMS), PS streaming services, 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 the entry point for content provider MBMS transmissions, may be used to authorize and initiate MBMS bearer services within a public land mobile network (PLMN), and may be used to schedule MBMS transmissions. The MBMS gateway 168 may be used to distribute MBMS services to base stations 102 belonging to a multicast broadcast single frequency network (MBSFN) area that broadcasts a specific service, and may be responsible for session management (start / stop) and collecting charging information related to eMBMS.

[0038] The core network 190 may include an access and mobility management function (AMF) 192, other AMFs 193, a session management function (SMF) 194, and a user plane function (UPF) 195. The AMF 192 may communicate with a unified data management (UDM) 196. The AMF 192 is a control node that handles signaling between the UE 104 and the core network 190. Typically, the AMF 192 provides QoS flow and session management. All user Internet Protocol (IP) packets are transmitted through the UPF 195. The UPF 195 provides UE IP address allocation and other functions. The UPF 195 is connected to the IP services 197. The IP services 197 may include the Internet, the intranet, the IP multimedia subsystem (IMS), packet switched (PS) streaming (PSS) services, and / or other IP services.

[0039] A base station may include and / or be referred to as a gNB, Node B, eNB, access point, base transceiver station, radio base station, radio transceiver, transceiver functionality, basic service set (BSS), extended service set (ESS), transmit receive point (TRP), or some other suitable terminology. Base station 102 provides an access point to EPC 160 or core network 190 for UE 104. Examples of UE 104 include a cellular phone, a smartphone, 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., an MP3 player), a camera, a game console, a tablet, a smart device, a wearable device, a vehicle, an electric meter, a gas pump, a large or small kitchen appliance, a healthcare device, an implant, a sensor / actuator, a display, or any other similarly functional device. Some of UE 104 may be referred to as IoT devices (e.g., a parking meter, a gas pump, a toaster, a vehicle, a heart monitor, etc.). 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 communication 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.

[0040] refer to Figure 1In certain aspects, the UE 104 may include a receiving component 198 configured to receive an instruction from a base station to enter an RRC inactive state. The receiving component 198 may also be configured to determine to enter a two-step random access channel (RACH) procedure in the radio resource control (RRC) inactive state. The receiving component 198 may also be configured to determine to transmit uplink data in a payload of a message A (MsgA) of the two-step RACH procedure. The receiving component 198 may also be configured to transmit MsgA of the two-step RACH procedure, the MsgA including a payload including at least uplink data. The receiving component 198 may also be configured to monitor for a message B (MsgB) of the two-step RACH procedure. The receiving component 198 may also be configured to receive MsgB of the two-step RACH procedure, wherein MsgB includes a fallback indication including a fallback random access response (RAR). Receiving component 198 may also be configured to retransmit the payload of MsgA upon receiving MsgB including a backoff indication. Receiving component 198 may also be configured to transmit Message 3 (Msg3) after receiving MsgB including a backoff indication, wherein hybrid automatic repeat request (HARQ) retransmission is applied to Msg3. Receiving component 198 may also be configured to monitor Message 4 (Msg4) after transmitting Msg3. Receiving component 198 may also be configured to receive Msg4, wherein Msg4 includes at least one of preconfigured uplink resources (PUR) or downlink data. Receiving component 198 may also be configured to store the uplink data in at least one buffer, wherein the payload of the retransmitted MsgA or the retransmitted payload of MsgA includes at least one of an RRC message or a data request message. The receiving component 198 may also be configured to retransmit MsgA when MsgB or Msg4 is not received, the retransmitted MsgA including a payload and a preamble, wherein the retransmitted MsgA includes at least one of an RRC message or a data request message. The receiving component 198 may also be configured to switch from a two-step RACH procedure to a four-step RACH procedure when MsgA is retransmitted at least a configured threshold number of retransmissions. The receiving component 198 may also be configured to select one or more preamble groups of the four-step RACH procedure, wherein the transport block (TB) size of each of the one or more preamble groups of the four-step RACH procedure is different from the TB size of each of the one or more preamble groups of the two-step RACH.

[0041] Reference again Figure 1In certain aspects, the base station 180 may include a transmitting component 199 configured to transmit an instruction to at least one user equipment (UE) to enter a radio resource control (RRC) inactive state. The transmitting component 199 may also be configured to receive a message A (MsgA) of a two-step random access channel (RACH) procedure, the MsgA including a payload including at least uplink data. The transmitting component 199 may also be configured to receive the retransmitted payload of MsgA when transmitting MsgB including a backoff indication. The transmitting component 199 may also be configured to transmit a message B (MsgB) of the two-step RACH procedure. The transmitting component 199 may also be configured to receive a message 3 (Msg3) after transmitting MsgB including the backoff indication, wherein hybrid automatic repeat request (HARQ) retransmission is applied to Msg3. The transmitting component 199 may also be configured to transmit a message 4 (Msg4), wherein the Msg4 includes at least one of pre-configured uplink resources (PUR) or downlink data. The transmitting component 199 may also be configured to receive a retransmitted MsgA including a payload and a preamble, wherein the retransmitted MsgA includes at least one of an RRC message or a data request message.

[0042] Although the following description may focus on 5G NR, the concepts described herein may be applicable to other similar areas such as LTE, LTE-A, CDMA, GSM, and other wireless technologies.

[0043] Figure 2A FIG2 is a diagram 200 illustrating an example of a first subframe within a 5G NR frame structure. Figure 2B is a diagram 230 showing an example of DL channels within a 5G NR subframe. Figure 2C FIG250 is a diagram illustrating an example of a second subframe within a 5G NR frame structure. Figure 2D is a diagram 280 showing an example of UL channels within a 5G NR subframe. The 5G NR frame structure may be frequency division duplex (FDD), where for a particular set of subcarriers (carrier system bandwidth), subframes within the set of subcarriers are dedicated to either DL or UL, or may be time division duplex (TDD), where for a particular set of subcarriers (carrier system bandwidth), subframes within the set of subcarriers are dedicated to both DL and UL. Figure 2A 、 Figure 2CIn the example provided, it is assumed that the 5G NR frame structure is TDD, subframe 4 is configured with slot format 28 (primarily DL), where D is DL, U is UL, and F is flexible between DL / UL, and subframe 3 is configured with slot format 1 (all UL). Although subframes 3 and 4 are shown as having slot formats 1 and 28, respectively, any particular subframe can be configured with any of the various available slot formats 0-61. Slot formats 0 and 1 are DL and UL, respectively. Other slot formats 2-61 include a mix of DL, UL and flexible symbols. The UE is configured with the slot format (dynamically through DL control information (DCI), or semi-statically / statically through radio resource control (RRC) signaling) via the received slot format indicator (SFI). Note that the description below also applies to the 5G NR frame structure for TDD.

[0044] Other wireless communication technologies may have different frame structures and / or different channels. A frame (10ms) may be divided into 10 equally sized subframes (1ms). Each subframe may include one or more time slots. A subframe may also include mini-slots, which may include 7, 4, or 2 symbols. Each time slot may include 7 or 14 symbols depending on the time slot configuration. For time slot configuration 0, each time slot may include 14 symbols, while for time slot configuration 1, each time slot may include 7 symbols. The symbols on the DL may be cyclic prefix (CP) OFDM (CP-OFDM) symbols. The symbols on the UL may be CP-OFDM symbols (for high throughput scenarios) or discrete Fourier transform (DFT) spread OFDM (DFT-s-OFDM) symbols (also known as single carrier frequency division multiple access (SC-FDMA) symbols) (for power-limited scenarios; limited to single-stream transmission). The number of time slots within a subframe is based on the time slot configuration and numerology. For slot configuration 0, different numerologies μ0 to 4 allow for 1, 2, 4, 8, and 16 slots per subframe, respectively. For slot configuration 1, different numerologies 0 to 2 allow for 2, 4, and 8 slots per subframe, respectively. Thus, for slot configuration 0 and numerology μ, there are 14 symbols per slot and 2μ slots per subframe. The subcarrier spacing and symbol length / duration are functions of the numerology. The subcarrier spacing can be equal to 2 μ *15kHz, where μ is a numerology of 0 to 4. Thus, numerology μ=0 has a subcarrier spacing of 15kHz, and numerology μ=4 has a subcarrier spacing of 240kHz. Symbol length / duration is inversely proportional to the subcarrier spacing. Figures 2A to 2DAn example of slot configuration 0 is provided, where there are 14 symbols per slot and the numerology μ=2, where there are 4 slots per subframe. The slot duration is 0.25 ms, the subcarrier spacing is 60 kHz, and the symbol duration is approximately 16.67 μs. Within a set of frames, there may be one or more different bandwidth parts (BWPs) (see Figure 2B ), which are frequency division multiplexed. Each BWP can have a specific numerology.

[0045] The resource grid can be used to represent the frame structure. Each time slot consists of a resource block (RB) (also called a physical RB (PRB)), which extends over 12 consecutive subcarriers. The resource grid is divided into multiple resource elements (REs). The number of bits carried by each RE depends on the modulation scheme.

[0046] like Figure 2A As shown, some of the REs carry reference (pilot) signals (RS) for the UE. The RSs may include a demodulation RS (DM-RS) (indicated as R for a particular configuration, but other DM-RS configurations are possible) and a channel state information reference signal (CSI-RS) used for channel estimation at the UE. The RSs may also include a beam measurement RS (BRS), a beam refinement RS (BRRS), and a phase tracking RS (PT-RS).

[0047] Figure 2BExamples of various DL channels within a subframe of a frame are shown. The physical downlink control channel (PDCCH) carries DCI within one or more control channel elements (CCEs) (e.g., 1, 2, 4, 8, or 16 CCEs), each CCE comprising six RE groups (REGs), each REG comprising 12 consecutive REs within an OFDM symbol of a RB. The PDCCH within a BWP may be referred to as a control resource set (CORESET). During a PDCCH monitoring opportunity for the CORESET, the UE is configured to monitor PDCCH candidates in a PDCCH search space (e.g., common search space, UE-specific search space), where the PDCCH candidates have different DCI formats and different aggregation levels. Additional BWPs may be located at higher and / or lower frequencies across the channel bandwidth. The primary synchronization signal (PSS) may be within symbol 2 of a particular subframe of a frame. The UE 104 uses the PSS to determine subframe / symbol timing and physical layer identity. The secondary synchronization signal (SSS) may be within symbol 4 of a particular subframe of a frame. The UE uses the SSS to determine the 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 the physical cell identifier (PCI). Based on the PCI, the UE can determine the position of the above-mentioned DM-RS. The physical broadcast channel (PBCH) carrying the master information block (MIB) can be logically grouped with the PSS and SSS to form a synchronization signal (SS) / PBCH block (also known as SS block (SSB)). The MIB provides multiple RBs in the system bandwidth 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 the system information block (SIB)) and paging messages.

[0048] like Figure 2C As shown, some of the REs carry DM-RS (indicated as R for a specific configuration, but other DM-RS configurations are also possible) for channel estimation at the base station. The UE can transmit DM-RS for the physical uplink control channel (PUCCH) and DM-RS for the physical uplink shared channel (PUSCH). The PUSCH DM-RS can be transmitted in the first one or two symbols of the PUSCH. The PUCCH DM-RS can be transmitted in different configurations, depending on whether a short PUCCH or a long PUCCH is transmitted and on the specific PUCCH format used. The UE can transmit a sounding reference signal (SRS). The SRS can be transmitted in the last symbol of the subframe. The SRS can have a comb structure, and the UE can transmit the SRS on one of the comb structures. The SRS can be used by the base station for channel quality estimation to achieve frequency-dependent scheduling on the UL.

[0049] Figure 2DExamples of various UL channels within a subframe of a frame are shown. The PUCCH may be positioned as indicated in one configuration. The PUCCH carries uplink control information (UCI), such as scheduling requests, channel quality indicator (CQI), precoding matrix indicator (PMI), rank indicator (RI), and hybrid automatic repeat request (HARQ) ACK / NACK feedback. The PUSCH carries data and may additionally be used to carry buffer status reports (BSRs), power headroom reports (PHRs), and / or UCI.

[0050] Figure 3 3 is a block diagram of a base station 310 communicating 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 functions. Layer 3 includes a radio resource control (RRC) layer, and Layer 2 includes a service data adaptation protocol (SDAP) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The controller / processor 375 provides RRC layer functions associated with broadcasting of system information (e.g., MIB, SIB), RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), inter-radio access technology (RAT) mobility, and measurement configuration for UE measurement reporting; PDCP layer functions associated with header compression / decompression, security (ciphering, deciphering, integrity protection, integrity verification), and handover support functions; RLC layer functions associated with transmission of upper layer packet data units (PDUs), error correction through ARQ, concatenation, segmentation, and reassembly of RLC service data units (SDUs), resegmentation of RLC data PDUs, and reordering of RLC data PDUs; MAC layer functions associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto transport blocks (TBs), demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel priority.

[0051] The transmit (TX) processor 316 and receive (RX) processor 370 implement Layer 1 functions associated with various signal processing functions. Layer 1, which includes the physical (PHY) layer, may include error detection on the transport channel, forward error correction (FEC) encoding / decoding of the transport channel, interleaving, rate matching, mapping onto the physical channel, modulation / demodulation of the physical channel, and MIMO antenna processing. The TX processor 316 handles the mapping to the signal constellation based on various modulation schemes (e.g., binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), M-phase shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The coded and modulated symbols are then separated into parallel streams. Each stream is then mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., a pilot) in the time and / or frequency domain, and then combined using an inverse fast Fourier transform (IFFT) to produce a physical channel carrying the 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 schemes, as well as for spatial processing. The channel estimates 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 corresponding spatial stream for transmission.

[0052] At the UE 350, each receiver 354RX receives a signal via its corresponding antenna 352. Each receiver 354RX recovers the information modulated onto the RF carrier and provides the information to a receive (RX) processor 356. The TX processor 368 and the RX processor 356 implement Layer 1 functions associated with various signal processing functions. The RX processor 356 can perform spatial processing on the information to recover any spatial streams destined for the UE 350. If multiple spatial streams are destined for the UE 350, they can be combined into a single OFDM symbol stream by the RX processor 356. 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 includes a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols and reference signals on each subcarrier are recovered and demodulated by determining the most likely signal constellation point transmitted by the base station 310. These soft decisions can be based on channel estimates calculated by the channel estimator 358. The soft decisions are then decoded and deinterleaved to recover the data and control signals originally transmitted on the physical channel by base station 310. The data and control signals are then provided to a controller / processor 359, which implements Layer 3 and Layer 2 functionality.

[0053] The controller / processor 359 may be associated with a memory 360 that stores program codes and data. The memory 360 may be referred to as a computer-readable medium. In the UL, the controller / processor 359 provides demultiplexing between transport and logical channels, packet reassembly, decryption, 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.

[0054] Similar to the functions described in conjunction with DL transmissions performed by the base station 310, the controller / processor 359 provides RRC layer functions associated with system information (e.g., MIB, SIB) acquisition, RRC connection, and measurement reporting; PDCP layer functions associated with header compression / decompression and security (encryption, decryption, integrity protection, integrity verification); RLC layer functions associated with transmission of upper layer PDUs, error correction through ARQ, concatenation, segmentation and reassembly of RLC SDUs, resegmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functions associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel priority.

[0055] The TX processor 368 may select an appropriate coding and modulation scheme and facilitate spatial processing using channel estimates derived by the channel estimator 358 from a reference signal or feedback transmitted from the base station 310. The spatial streams generated by the TX processor 368 may be provided to different antennas 352 via separate transmitters 354TX. Each transmitter 354TX may modulate an RF carrier with a corresponding spatial stream for transmission.

[0056] UL transmissions are processed at the base station 310 in a manner similar to that described in conjunction with the receiver functionality 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.

[0057] The controller / processor 375 may be associated with a memory 376 that stores program codes and data. The memory 376 may be referred to as a computer-readable medium. In the UL, the controller / processor 375 provides demultiplexing between transport and logical channels, packet reassembly, decryption, header decompression, and control signal processing to recover IP packets from the UE 350. The IP packets from the controller / processor 375 may be provided to the EPC 160. The controller / processor 375 is also responsible for error detection using an ACK and / or NACK protocol to support HARQ operations.

[0058] At least one of the TX processor 368, the RX processor 356, and the controller / processor 359 may be configured to perform operations related to Figure 1 198 related aspects.

[0059] At least one of the TX processor 316, the RX processor 370, and the controller / processor 375 may be configured to perform operations related to Figure 1 199 related aspects.

[0060] Some aspects of wireless communications include different states for user equipment (UE), such as data transmission in a radio resource control (RRC) inactive (RRC-INACTIVE) state. In some aspects, a UE may generate a small amount of data, i.e., small data, in bursts in a data session. This type of traffic may be applicable to every vertical application, including mobile broadband (MBB) and the Internet of Things (IoT), such as instant messaging software, social media software, and / or wearable IoT devices. In some instances, a network or base station may allow a UE to transmit uplink data in an RRC-INACTIVE state without the UE having to transition to an RRC connected (RRC_CONNECTED) state. A network or base station may also include multiple targets for data transmission. For example, an uplink (UL) small data transmission (SDT) for a random access channel (RACH)-based scheme, i.e., a two-step (2-step) RACH or a four-step (4-step) RACH, may correspond to an RRC_INACTIVE state.

[0061] In some aspects, the UE may receive an instruction to enter an RRC inactive state. The UE may then determine to enter a RACH procedure while in the RRC inactive state. Consequently, the UE may transmit a small amount of data, i.e., small data, in the RACH procedure while in the RRC inactive state. The base station may also instruct the UE to transition to an RRC connected state based on communications during the RRC inactive state. This may also be included in an RRC release message from the base station.

[0062] In the data transmission during the 2-step RACH, the UE can select the preamble configured for the data during the 2-step RACH (e.g., mobile originated (MO) data). For example, a small amount of data and an RRC message can be transmitted in message A (MsgA). In some instances, this can occur when the UL grant of MsgA is large enough to handle the data. MsgA can include a preamble, user data, uplink data (e.g., PUSCH data), and an RRC message (i.e., an RRCResumeRequest message). Downlink (DL) data or response data for an application confirmation (ACK) in response to UL data and an RRC message (i.e., an RRCRelease message) can be scheduled in message B (MsgB).

[0063] MsgA of the 2-step RACH procedure may include a random access (RA) preamble on the physical RACH (PRACH) and a payload on the PUSCH. After MsgA is transmitted, the UE may monitor for a response from the network (e.g., MsgB) within the configured window. If the network successfully decodes the preamble but fails to decode the payload of MsgA, the network may send a fallback indication, i.e., a fallback random access response (RAR), in MsgB. In some aspects, the payload of MsgA may not be decoded due to the payload size. MsgB may instruct the UE to transmit Message 3 (Msg3) to retransmit the MsgA payload and further monitor for contention resolution in Message 4 (Msg4). The aforementioned procedure may be referred to as a fallback procedure.

[0064] In some instances, the preamble index in the medium access control (MAC) header or MAC subheader of the fallback RAR can identify whether MsgB corresponds to a certain UE. The network can send a fallback indication (i.e., fallbackRAR) in MsgB to instruct the UE to execute Msg3 to retransmit the MsgA payload and further monitor contention resolution in Msg4. For example, if contention resolution is not successful after multiple Msg3 transmissions, the UE can retransmit MsgA. In addition, if the network does not decode the preamble or payload of MsgA and the UE does not receive any response within the configured time window, the UE can retransmit MsgA.

[0065] If the random access procedure with 2-step RACH is not completed after multiple MsgA transmissions (i.e., MsgA transmission maximum (msgA_TransMax), the UE can be configured to switch the RA procedure. For example, after multiple MsgA transmissions, the UE can switch to a 4-step contention-based random access (CBRA) procedure. This 4-step CBRA may include a first message (Msg1) to be transmitted from the UE.

[0066] Based on the above, there is a need for improved data transmission solutions during RA procedures in the RRC Inactive state. During a 2-step RACH procedure when the UE is in the RRC Inactive state, it is necessary to perform small data transmissions in a fallback procedure or MsgA retransmission procedure. For example, it is currently necessary to define UE behavior in response to the fallback procedure during a 2-step RACH procedure.

[0067] Aspects of the present disclosure may include small data transmission during an RA procedure, such as in an RRC inactive state. In some aspects, during a 2-step RACH procedure when the UE is in an RRC inactive state, aspects of the present disclosure may perform small data transmission in a fallback procedure or an MsgA retransmission procedure. For example, the present disclosure may define UE behavior, such as data transmission, in response to a fallback procedure during a RACH procedure (e.g., a 2-step RACH).

[0068] In some aspects, the present disclosure may include a 2-step RACH fallback procedure. If the network sends a fallback indication, i.e., a fallback RAR, in MsgB, the UE may retransmit the payload of MsgA in message 3 (Msg3) and monitor contention resolution in message 4 (Msg4). The payload of MsgA may include an RRC message and user data or uplink data. In some instances, hybrid automatic repeat request (HARQ) retransmission may be allowed in Msg3 to obtain user data or uplink data. In addition, in the fallback case, the redundancy version (RV) may be equal to zero for the Msg3 transmission. In addition, the TB size in the UL grant in the fallback RAR may be the same as the TB size in the payload transmission in MsgA. In addition, if there is a high contention scenario, the UE may have a reduced chance to successfully transmit data.

[0069] Figure 4 FIG4 is a diagram 400 illustrating exemplary communications between a UE 402 and a base station 404 according to one or more techniques of this disclosure. Figure 4 As shown, diagram 400 includes MO data during a 2-step RACH in a fallback situation. Figure 4 UE 402 is shown remaining in the RRC_INACTIVE state for a certain amount of time.

[0070] like Figure 4As shown, at step 410, UE 402 may send an RRC recovery request and UL data in MsgA. UE 402 may then monitor the fallback RAR in MsgB. At step 420, UE 402 may receive the fallback RAR from base station 404 via MsgB. At step 430, UE 402 may retransmit the payload of MsgA in Msg3, which may include an RRC recovery request message and user UL data in the payload of MsgA. UE 402 may then monitor the RRC release message and DL data in Msg4. At step 440, UE 402 may receive the RRC release message and DL data from base station 404 in Msg4.

[0071] Aspects of the present disclosure may include an additional 2-step RACH fallback procedure. If the network or base station sends a fallback indication, i.e., a fallback RAR, in MsgB, the UE may retransmit a portion of the payload of MsgA in Msg3 and monitor contention resolution in Msg4. If the transmitted data can be handled by an UL grant, a portion of the payload of MsgA may include a portion of user data. The UE may also store all or part of the user data or UL data in a buffer, and the UE may retransmit an RRC message from the original MsgA payload, i.e., RRCResumeRequest, in Msg3. The network may respond to cause the UE to transition to an RRC-CONNECTED state for subsequent user data transmission. In addition, the UE may transmit an RRC message and a data request message or a small data request message. The data request message may be a MAC-CE and / or RRC message of a smaller size (i.e., compared to the original payload of MsgA). If the network configures pre-configured uplink resources (PUR) in Msg4, the UE can transmit subsequent uplink packets in the pre-configured resources without entering the RRC_CONNECTED state. This can help the UE save power.

[0072] Figure 5 FIG. 5 is a diagram 500 illustrating exemplary communications between a UE 502 and a base station 504 according to one or more techniques of this disclosure. Figure 5 As shown, diagram 500 includes MO data during a 2-step RACH in a fallback situation. Figure 5 It shows that UE 502 remains in the RRC_INACTIVE state for a certain amount of time.

[0073] like Figure 5As shown, at step 510, UE 502 may send an RRC recovery request message and UL data in MsgA. UE 502 may then monitor the fallback RAR in MsgB. At step 520, UE 502 may receive the fallback RAR from base station 504 in MsgB. In addition, at step 530, UE 502 may retransmit the payload of MsgA in Msg3, which may include an RRC recovery request message and a small data request message, such as a MAC-CE and / or an updated RRC message. UE 502 may then monitor the RRC release message and preconfigured uplink resources (PUR) in Msg4. At step 540, UE 502 may receive the RRC release message and PUR from base station 504 in Msg4.

[0074] In some aspects, after a 2-step RACH fallback, if contention resolution is not successful after multiple Msg3 transmissions or after an MsgA transmission, the network may be unable to decode the preamble and / or payload of MsgA. As a result, the base station may be unable to provide a response within the configured time window. When this occurs, the UE may revert to MsgA transmission. Additionally, when retransmitting MsgA, the MsgA payload may be transmitted without any modification. The MsgA payload may include RRC messages and user data. During retransmission, the MsgA preamble index and preamble group may not be modified. Additionally, for MsgAPUSCH initial transmissions and MsgA retransmissions, the RV may be equal to zero. Since the first MsgA transmission may fail and if this is a high contention scenario, the UE may have a reduced chance of successfully transmitting data in the MsgA retransmission.

[0075] Figure 6 FIG6 is a diagram 600 illustrating exemplary communications between a UE 602 and a base station 604 according to one or more techniques of this disclosure. Figure 6 As shown, diagram 600 includes MO data during a 2-step RACH in a MsgA retransmission scenario. Figure 6 Display 600 includes a MsgBRAR window.

[0076] like Figure 6As shown, at step 610, UE 602 may transmit an RRC resume request message and UL data in MsgA. UE 602 may then monitor MsgB. If the network or base station does not provide a response within the configured window and does not decode the preamble and / or payload of MsgA, UE 602 may retransmit MsgA, which may include the RRC resume request message and UL data, at step 630. UE 602 may then monitor MsgB. At step 640, UE 602 may receive MsgB, which includes an RRC release message and DL data.

[0077] In some instances, when MsgA is retransmitted, the MsgA payload may not be modified. The MsgA payload may include an RRC message and / or user data or UL data. In addition, the UE may reselect a new preamble index and / or a new preamble group for the preamble of MsgA during MsgA retransmission. The new preamble index and / or the new preamble group may be mapped to PUSCH resources with larger UL grant resources. This may increase the likelihood that the UE will successfully transmit small data or uplink data. Therefore, during MsgA retransmission, the UE may reselect a new preamble index or one or more new preamble groups including the preamble index.

[0078] In some aspects, after the 2-step RACH fallback procedure, if contention resolution is unsuccessful after the transmission of Msg3 or MsgA, the network may not respond within the configured time window and may be unable to decode the preamble and / or payload of MsgA. When this occurs, the UE may retransmit MsgA. When retransmitting MsgA, the UE may store UL data or user data in a buffer and retransmit the RRC message from the original MsgA, namely, RRCResumeRequest. The network may instruct the UE to transition to the RRC-CONNECTED state for subsequent user data transmission.

[0079] As indicated herein, when retransmitting MsgA, the UE may store the user data or a portion of the user data in at least one buffer and / or transmit a portion of the user data in MsgA. The small data request message may be a MAC-CE and / or RRC message with a smaller size. The network may configure preconfigured uplink resources (PUR) in MsgB, and the UE may then transmit subsequent uplink data packets in the preconfigured resources without entering the RRC-CONNECTED state, which may save power at the UE. Additionally, the UE may select a new preamble index or preamble group that may be mapped to PUSCH resources with a larger UL grant resource.

[0080] Figure 7 FIG. 7 is a diagram 700 illustrating exemplary communications between a UE 702 and a base station 704 according to one or more techniques of this disclosure. Figure 7 As shown, diagram 700 includes MO data during a 2-step RACH in a MsgA retransmission scenario. Figure 7 Display 700 includes a MsgBRAR window.

[0081] like Figure 7 As shown, UE 702 may send an RRC recovery request and UL data in MsgA. UE 702 may then monitor MsgB. If the network or base station does not decode the preamble and payload of MsgA and does not provide a response within a configured time window (e.g., an RAR window), UE 702 may retransmit MsgA at step 730. The retransmitted MsgA may include an RRC recovery request message, a portion of user data, and / or a data request message (e.g., a MAC-CE and an RRC message). UE 702 may then monitor MsgB. At step 740, UE 702 may receive MsgB, including an RRC release message and / or a PUR.

[0082] In some aspects, a 2-step RACH procedure may be switched to a 4-step RACH procedure. If a random access procedure with a 2-step RA procedure is not completed after multiple MsgA transmissions (e.g., a MsgA transmission maximum (msgA-TransMax), the UE may be configured to switch to a CBRA procedure with a 4-step RA, which may include Msg1 of a 4-step CBRA procedure. For example, the UE may select a 4-step RACH preamble group that is different from the 2-step RACH preamble group. Additionally, the transport block (TB) size in the 4-step RACH preamble group may be larger than the TB size in the 2-step RACH preamble group. Additionally, the TB size in the UL grant in Msg2RAR in the 4-step RACH procedure may be larger than the TB size of the payload transmission in MsgA in the 2-step RACH. In some instances, this may occur when a different 4-step preamble group is selected when switching to the 4-step RACH.

[0083] Figure 8 8 is a diagram 800 illustrating exemplary communications between a UE 802 and a base station 804 .

[0084] At 810, base station 804 may transmit an instruction, such as instruction 814, to at least one UE (e.g., UE 802) to enter a radio resource control (RRC) inactive state. At 812, UE 802 may receive an instruction, such as instruction 814, from base station 804 to enter an RRC inactive state. At 816, UE 802 may determine to enter a two-step random access channel (RACH) procedure in the radio resource control (RRC) inactive state. At 818, UE 802 may determine to transmit uplink data in a payload of message A (MsgA) of the two-step RACH procedure.

[0085] At 820, UE 802 may transmit a MsgA (e.g., MsgA 824) of a two-step RACH procedure, the MsgA including a payload including at least uplink data. At 822, base station 804 may receive a message A (MsgA) (e.g., MsgA 824) of a two-step random access channel (RACH) procedure, the MsgA including a payload including at least uplink data. In some aspects, the payload of the MsgA includes at least one of an RRC message or a data request message, the MsgA including a preamble associated with one of the one or more preamble groups.

[0086] At 828, UE 802 may monitor for Message B (MsgB) of a two-step RACH procedure.

[0087] At 830, base station 804 may transmit a message B (MsgB) of a two-step RACH procedure, such as MsgB 834. At 832, UE 802 may receive MsgB of the two-step RACH procedure, such as MsgB 834, wherein MsgB includes a fallback indication, including a fallback random access response (RAR). At 835, UE 802 may store uplink data or a portion of the uplink data in at least one buffer. At 836, UE 802 may retransmit the payload of MsgA upon receiving MsgB including the fallback indication. At 838, base station 804 may receive the retransmitted payload of MsgA upon transmitting MsgB including the fallback indication.

[0088] At 840, UE 802 may transmit a message 3 (Msg3) (e.g., Msg3 844) after receiving MsgB including a backoff indication, wherein hybrid automatic repeat request (HARQ) retransmission is applied to Msg3. At 842, base station 804 may receive a message 3 (Msg3) (e.g., Msg3 844) after transmitting MsgB including a backoff indication, wherein hybrid automatic repeat request (HARQ) retransmission is applied to Msg3. In some aspects, Msg3 may include a portion of the payload of MsgA, wherein the portion of the payload of MsgA corresponds to at least one of an RRC message or at least a portion of uplink data, wherein the uplink data is user data. The uplink data or the portion of the uplink data may be stored in at least one buffer. Additionally, Msg3 may include at least one of an RRC message or a data request message, wherein the data request message is at least one of a medium access control (MAC) control element (MAC-CE) or an RRC message.

[0089] At 850, UE 802 may monitor for message 4 (Msg4) after transmitting Msg3. At 860, base station 804 may transmit message 4 (Msg4) (e.g., Msg4 864), where Msg4 includes at least one of pre-configured uplink resources (PUR) or downlink data. At 862, UE 802 may receive Msg4 (e.g., Msg4 864), where Msg4 includes at least one of pre-configured uplink resources (PUR) or downlink data.

[0090] At 870, UE 802 may store the uplink data or a portion of the uplink data in at least one buffer, wherein the payload of the retransmitted MsgA or the retransmitted payload of MsgA includes at least one of an RRC message or a data request message.

[0091] At 880, UE 802 may retransmit MsgA (e.g., retransmitted MsgA 884) when not receiving MsgB or Msg4, the retransmitted MsgA including a payload and a preamble, wherein the retransmitted MsgA includes at least one of an RRC message, a data request message, or at least a portion of uplink data, wherein the uplink data is user data. At 882, base station 804 may receive the retransmitted MsgA (e.g., retransmitted MsgA 884) including a payload and a preamble, wherein the retransmitted MsgA includes at least one of an RRC message or a data request message. UE 802 may also select at least one of one or more new preamble groups or new preambles for the retransmitted MsgA.

[0092] At 890, the UE 802 may switch from the two-step RACH procedure to the four-step RACH procedure when MsgA is retransmitted for at least a configured threshold number of retransmissions. At 892, the UE 802 may select one or more preamble groups for the four-step RACH procedure, wherein a transport block (TB) size for each of the one or more preamble groups for the four-step RACH procedure is different from a TB size for each of the one or more preamble groups for the two-step RACH.

[0093] Figure 9 900 is a flowchart of a method of wireless communication. The method may be performed by a UE or a component thereof (e.g., UE 104, 350, 802; device 1102; a processing system, which may include memory 360 and may be the entire UE or a component thereof, such as TX processor 368, controller / processor 359, transmitter 354TX, antenna 352, and / or the like). Optional aspects are shown in dashed lines. The methods described herein may provide numerous benefits, such as improved communication signaling, resource utilization, and / or power savings.

[0094] At 902, the apparatus may receive an instruction from a base station to enter an RRC inactive state, such as in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 902 may be performed by the determining component 1140 .

[0095] At 904, the apparatus may determine to enter a two-step random access channel (RACH) procedure in a radio resource control (RRC) inactive state, such as in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 904 can be performed by the determining component 1140.

[0096] At 905, the apparatus may determine to transmit uplink data in a payload of message A (MsgA) of a two-step RACH procedure, such as in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 As described in the examples.

[0097] At 906, the apparatus may transmit a MsgA of a two-step RACH procedure, the MsgA including a payload including at least uplink data, such as in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 906 may be performed by determining component 1140. In some aspects, the payload of MsgA may include at least one of an RRC message or a data request message, the MsgA including a preamble associated with one of the one or more preamble groups, as described in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 As described in the examples.

[0098] At 908, the apparatus may monitor for message B (MsgB) of a two-step RACH procedure, such as in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 908 can be performed by the determining component 1140.

[0099] At 910, the apparatus may receive a MsgB of a two-step RACH procedure, wherein the MsgB includes a fallback indication including a fallback random access response (RAR), such as in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 910 may be performed by determining component 1140. At 911, the apparatus may store the uplink data in at least one buffer, as in combination with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 As described in the examples.

[0100] At 912, the apparatus may retransmit the payload of MsgA upon receiving MsgB including a backoff indication, as in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 912 can be performed by the determining component 1140.

[0101] At 914, the apparatus may transmit a message 3 (Msg3) after receiving MsgB including a backoff indication, wherein hybrid automatic repeat request (HARQ) retransmission is applied to Msg3, as in combination with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 914 can be performed by the determining component 1140.

[0102] At 916, the device may monitor for message 4 (Msg4) after transmitting Msg3, as shown in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 916 may be performed by determining component 1140. In some aspects, Msg3 may include a portion of the payload of MsgA, the portion of the payload of MsgA corresponding to at least one of an RRC message or at least a portion of uplink data, wherein the uplink data is user data, as described in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 In addition, Msg3 may include at least one of an RRC message or a data request message, wherein the data request message is at least one of a medium access control (MAC) control element (MAC-CE) or an RRC message, as described in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 As described in the examples.

[0103] At 918, the apparatus may receive Msg4, wherein Msg4 includes at least one of preconfigured uplink resources (PUR) or downlink data, such as in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 918 can be performed by the determining component 1140.

[0104] At 920, the apparatus may store uplink data in at least one buffer, wherein the payload of the retransmitted MsgA or the retransmitted payload of MsgA comprises at least one of an RRC message or a data request message, as in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 920 may be performed by the determining component 1140 .

[0105] At 922, the apparatus may retransmit MsgA when MsgB or Msg4 is not received, the retransmitted MsgA including a payload and a preamble, wherein the retransmitted MsgA includes at least one of an RRC message, a data request message, or at least a portion of uplink data, wherein the uplink data is user data, as described in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 922 may be performed by the determining component 1140. In addition, the apparatus may select at least one of one or more new preamble groups or new preambles for the retransmitted MsgA, as described in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 As described in the examples.

[0106] At 924, the apparatus may switch from a two-step RACH procedure to a four-step RACH procedure when MsgA is retransmitted at least a configured threshold number of retransmissions, such as in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 924 can be performed by the determining component 1140.

[0107] At 926, the apparatus may select one or more preamble groups for a four-step RACH procedure, wherein a transport block (TB) size of each of the one or more preamble groups for the four-step RACH procedure is different from a TB size of each of the one or more preamble groups for the two-step RACH procedure, as described in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 926 can be performed by the determining component 1140.

[0108] Figure 10 1000 is a flowchart of a method of wireless communication. The method may be performed by a base station or a component of a base station (e.g., base station 102, 180, 310, 804; device 1202; a processing system, which may include memory 376 and may be the entire base station or a component of a base station, such as antenna 320, receiver 318RX, RX processor 370, controller / processor 375, and / or the like). Optional aspects are shown in dashed lines. The methods described herein may provide numerous benefits, such as improved communication signaling, resource utilization, and / or power conservation.

[0109] At 1002, the apparatus may transmit an instruction to at least one UE to enter a radio resource control (RRC) inactive state, such as in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 1002 may be performed by the determining component 1240 .

[0110] At 1004, the apparatus may receive a message A (MsgA) of a two-step random access channel (RACH) procedure, the MsgA including a payload including at least uplink data, such as in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 1004 may be performed by determining component 1240. In some aspects, the payload of MsgA may include at least one of an RRC message or a data request message, the MsgA including a preamble associated with one of the one or more preamble groups, as described in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 As described in the examples.

[0111] At 1006, the apparatus may receive the retransmitted payload of MsgA while transmitting MsgB including a backoff indication, as in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 1006 can be performed by the determining component 1240.

[0112] At 1008, the apparatus may transmit a message B (MsgB) of a two-step RACH procedure, such as in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 1008 may be performed by determining component 1240. In some instances, MsgB may include a fallback indication, the fallback indication including a fallback random access response (RAR), such as in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 As described in the examples.

[0113] At 1010, the apparatus may receive a message 3 (Msg3) after transmitting MsgB including a backoff indication, wherein hybrid automatic repeat request (HARQ) retransmission is applied to Msg3, as in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 1010 may be performed by determining component 1240. In some aspects, Msg3 may include a portion of a payload of MsgA, wherein the portion of the payload of MsgA corresponds to at least one of an RRC message or at least a portion of uplink data, wherein the uplink data is user data, as described in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 In addition, Msg3 may include at least one of an RRC message or a data request message, wherein the data request message is at least one of a medium access control (MAC) control element (MAC-CE) or an RRC message, as described in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 As described in the examples.

[0114] At 1012, the apparatus may transmit a message 4 (Msg4), wherein the Msg4 includes at least one of a preconfigured uplink resource (PUR) or downlink data, as in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 1012 can be performed by the determining component 1240.

[0115] At 1014, the apparatus may receive a retransmitted MsgA including a payload and a preamble, wherein the retransmitted MsgA includes at least one of an RRC message, a data request message, or at least a portion of uplink data, wherein the uplink data is user data, as described in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 For example, 1014 may be performed by determining component 1240. In some aspects, the retransmitted MsgA may include at least one of one or more new preamble groups or new preambles, such as in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 In addition, the payload of the retransmitted MsgA or the retransmitted payload of MsgA may include at least one of an RRC message or a data request message, as described in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 In addition, when the retransmitted MsgA is received, the two-step RACH procedure can be switched to the four-step RACH procedure, as shown in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 Furthermore, the four-step RACH procedure may include one or more preamble groups, wherein a transport block (TB) size of each of the one or more preamble groups of the four-step RACH procedure is different from a TB size of each of the one or more preamble groups of the two-step RACH, as described in conjunction with Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 As described in the examples.

[0116] Figure 11FIG1 is a diagram 1100 illustrating an example of a hardware implementation for an apparatus 1102. Apparatus 1102 is a UE and includes a cellular baseband processor 1104 (also known as a modem) coupled to a cellular RF transceiver 1122 and one or more subscriber identity module (SIM) cards 1120, an application processor 1106 coupled to a secure digital (SD) card 1108 and a screen 1110, a Bluetooth module 1112, a wireless local area network (WLAN) module 1114, a global positioning system (GPS) module 1116, and a power supply 1118. Cellular baseband processor 1104 communicates with UE 104 and / or BS 102 / 180 via cellular RF transceiver 1122. Cellular baseband processor 1104 may include computer-readable media / memory. The computer-readable media / memory may be non-transitory. Cellular baseband processor 1104 is responsible for general processing, including executing software stored on the computer-readable media / memory. The software, when executed by the cellular baseband processor 1104, causes the cellular baseband processor 1104 to perform the various functions described above. Computer-readable media / memory may also be used to store data that is manipulated by the cellular baseband processor 1104 when executing the software. The cellular baseband processor 1104 also includes a receiving component 1130, a communication manager 1132, and a transmitting component 1134. The communication manager 1132 includes one or more of the components shown. The components within the communication manager 1132 may be stored in a computer-readable medium / memory and / or configured as hardware within the cellular baseband processor 1104. The cellular baseband processor 1104 may be a component of the UE 350 and may include a memory 360 and / or at least one of a TX processor 368, an RX processor 356, and a controller / processor 359. In one configuration, the device 1102 may be a modem chip and include only the baseband processor 1104, and in another configuration, the device 1102 may be the entire UE (e.g., see Figure 3 350) and includes additional modules of device 1102.

[0117] The communications manager 1132 includes a determining component 1140 configured to determine to enter a two-step random access channel (RACH) procedure in a radio resource control (RRC) inactive state, e.g., as described above in connection with step 904. The determining component 1140 may also be configured to determine to transmit uplink data in a payload of message A (MsgA) of the two-step RACH procedure, e.g., as described above in connection with step 905. The determining component 1140 may also be configured to transmit MsgA of the two-step RACH procedure, the MsgA including a payload including at least uplink data, e.g., as described above in connection with step 906. The determining component 1140 may also be configured to monitor message B (MsgB) of the two-step RACH procedure, e.g., as described above in connection with step 908.

[0118] The apparatus may include executing Figure 8 and Figure 9 Each of the blocks in the algorithm in the above flowchart is an additional component. Therefore, Figure 8 and Figure 9 Each block in the above flowchart may be performed by a component, and the apparatus may include one or more of those components. The component may be one or more hardware components specifically configured to implement the process / algorithm, implemented by a processor configured to execute the process / algorithm, stored in a computer-readable medium for processor implementation, or some combination thereof.

[0119] In one configuration, the apparatus 1102, and specifically the cellular baseband processor 1104, includes means for determining to enter a two-step random access channel (RACH) procedure in a radio resource control (RRC) inactive state. The apparatus 1102 may also include means for determining to transmit uplink data in a payload of message A (MsgA) of the two-step RACH procedure. The apparatus 1102 may also include means for transmitting MsgA of the two-step RACH procedure, the MsgA including a payload including at least uplink data. The apparatus 1102 may also include means for monitoring message B (MsgB) of the two-step RACH procedure. The aforementioned means may be one or more of the aforementioned components of the apparatus 1102 configured to perform the functions recited by the aforementioned means. As described above, the apparatus 1102 may include a TX processor 368, an RX processor 356, and a controller / processor 359. Thus, in one configuration, the aforementioned means may be the TX Processor 368, RX Processor 356, and controller / processor 359 configured to perform the functions recited by the aforementioned means.

[0120] Figure 1212 is a diagram 1200 illustrating an example of a hardware implementation for an apparatus 1202. Apparatus 1202 is a base station and includes a baseband unit 1204. Baseband unit 1204 can communicate with UE 104 via cellular RF transceiver 822. Baseband unit 1204 may include computer-readable media / memory. Baseband unit 1204 is responsible for general processing, including executing software stored on the computer-readable media / memory. When executed by baseband unit 1204, the software causes baseband unit 1204 to perform the various functions described above. The computer-readable media / memory may also be used to store data manipulated by baseband unit 1204 when executing the software. Baseband unit 1204 also includes a receiving component 1230, a communication manager 1232, and a transmitting component 1234. Communication manager 1232 includes one or more of the components shown. Components within communication manager 1232 may be stored in computer-readable media / memory and / or configured as hardware within baseband unit 1204. The baseband unit 1204 may be a component of the BS 310 and may include a memory 376 and / or at least one of the TX processor 316 , the RX processor 370 , and the controller / processor 375 .

[0121] The communications manager 1232 includes a determining component 1240 configured to transmit an instruction to at least one UE to enter a radio resource control (RRC) inactive state, e.g., as described above in connection with step 1002. The determining component 1240 may also be configured to receive a message A (MsgA) of a two-step random access channel (RACH) procedure, the MsgA including a payload including at least uplink data, e.g., as described above in connection with step 1004. The determining component 1240 may also be configured to transmit a message B (MsgB) of a two-step RACH procedure, e.g., as described above in connection with step 1008.

[0122] The apparatus may include executing Figure 8 and Figure 10 Each of the blocks in the algorithm in the above flowchart is an additional component. Therefore, Figure 8 and Figure 10 Each block in the above flowchart may be performed by a component, and the apparatus may include one or more of those components. The component may be one or more hardware components specifically configured to implement the process / algorithm, implemented by a processor configured to execute the process / algorithm, stored in a computer-readable medium for processor implementation, or some combination thereof.

[0123] In one configuration, the apparatus 1202, and specifically the baseband unit 1204, includes means for transmitting an instruction to at least one user equipment (UE) to enter a radio resource control (RRC) inactive state. The apparatus 1202 may also include means for receiving a message A (MsgA) of a two-step random access channel (RACH) procedure, the MsgA including a payload including at least uplink data. The apparatus 1202 may also include means for transmitting a message B (MsgB) of a two-step RACH procedure. The aforementioned means may be one or more of the aforementioned components of the apparatus 1202 configured to perform the functions listed above. As described above, the apparatus 1202 may include a TX processor 316, an RX processor 370, and a controller / processor 375. Therefore, in one configuration, the aforementioned means may be the TX processor 316, the RX processor 370, and the controller / processor 375 configured to perform the functions listed above.

[0124] Additional disclosures are included in the appendix.

[0125] It should be understood that the specific order or hierarchy of blocks in the disclosed processes / flowcharts is illustrative of exemplary methods. Based on design preferences, it should be understood that the specific order or hierarchy of blocks in the processes / flowcharts may be rearranged. Furthermore, 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.

[0126] 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 apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects. Therefore, the claims are not intended to be limited to the aspects shown herein, but should be given a complete scope consistent with the language of the claims, wherein, unless otherwise specifically stated, reference to an element in the singular is not intended to mean "one and only one", but "one or more". The word "exemplary" is used herein to mean "serving as an example, instance, or illustration". Any aspect described as "exemplary" herein is not necessarily interpreted as being preferred or advantageous relative to other examples. Unless otherwise specifically stated, the term "some" refers to one or more. 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, C, or any combination thereof", includes any combination of A, B, and / or C, and can include multiples of A, multiples of B, or multiples of C. Specifically, terms 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,” “A, B, C, or any combination thereof” may be only A, only B, only C, A and B, A and C, B and C, or A and B and C, where any such combination may include one or more members of A, B, or C. All structural and functional equivalents to the elements of the various embodiments described throughout this disclosure that are known or later come to be known to one of ordinary skill in the art are expressly incorporated herein by reference and are intended to be covered by the claims. In addition, nothing disclosed herein is intended to be self-explanatory, regardless of whether such disclosure is explicitly stated in the claims. The words “module,” “mechanism,” “element,” “device,” etc. cannot replace the word “means.” Therefore, any claim element shall not be interpreted as a means-plus-function unless the element is expressly referenced using the phrase “means for….”

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Claims

1. An apparatus for wireless communication at a user equipment (UE), comprising: Memory; as well as at least one processor coupled to the memory and configured to: Determine to enter a two-step random access channel (RACH) procedure in a radio resource control (RRC) inactive state; Determining that uplink data is transmitted in the payload of message A MsgA of the two-step RACH procedure; transmitting a MsgA of the two-step RACH procedure, wherein the MsgA includes the payload, and the payload includes at least the uplink data; Monitoring message B MsgB of the two-step RACH procedure; retransmitting the MsgA when the MsgB is not received within a configured time window, the retransmitted MsgA including a payload and a preamble, wherein the payload of the retransmitted MsgA includes at least one of an RRC message or a data request message; as well as receiving a second MsgB in response to retransmitting the MsgA, the second MsgB including pre-configured uplink resources to enable transmission of subsequent uplink data without entering an RRC_CONNECTED state, One or more new preamble groups are selected for the retransmitted MsgA, wherein the one or more new preamble groups are mapped to physical uplink shared channel resources with larger uplink granted resources.

2. The apparatus of claim 1, wherein a payload of the MsgA comprises at least one of an RRC message or a data request message, the MsgA comprising a preamble associated with one of one or more preamble groups.

3. The apparatus of claim 1 , wherein the at least one processor is further configured to: A MsgB of the two-step RACH procedure is received, wherein the MsgB includes a fallback indication, and the fallback indication includes a fallback random access response RAR.

4. The apparatus of claim 3 , wherein the at least one processor is further configured to: The payload of the MsgA is retransmitted when the MsgB including the backoff indication is received.

5. The apparatus of claim 3 , wherein the at least one processor is further configured to: After receiving the MsgB including the backoff indication, a message 3 Msg3 is transmitted, wherein hybrid automatic repeat request HARQ retransmission is applied to Msg3.

6. The apparatus of claim 5, wherein the Msg3 includes a portion of a payload of the MsgA, the portion of the payload of the MsgA corresponding to at least one of an RRC message or at least a portion of the uplink data, wherein the uplink data is user data.

7. The apparatus of claim 5, wherein the Msg3 comprises at least one of an RRC message or a data request message, wherein the data request message is at least one of a Medium Access Control (MAC) Control Element (MAC-CE) or an RRC message.

8. The apparatus of claim 5, wherein the at least one processor is further configured to: After transmitting the Msg3, monitor for message 4 Msg4.

9. The apparatus of claim 8, wherein the at least one processor is further configured to: A Msg4 is received, wherein the Msg4 includes at least one of a pre-configured uplink resource PUR or downlink data.

10. The apparatus of claim 1 , wherein the at least one processor is further configured to: When the MsgA is retransmitted at least a configured threshold number of retransmissions, a switch is made from the two-step RACH procedure to a four-step RACH procedure.

11. The apparatus of claim 10, wherein the at least one processor is further configured to: One or more preamble groups of the four-step RACH procedure are selected, wherein a transport block (TB) size of each of the one or more preamble groups of the four-step RACH procedure is different from a TB size of each of the one or more preamble groups of the two-step RACH.

12. The apparatus of claim 1 , wherein the at least one processor is further configured to: The uplink data is stored in at least one buffer.

13. The apparatus of claim 1 , wherein the at least one processor is further configured to: An instruction to enter the RRC inactive state is received from the base station.

14. A method for wireless communication at a user equipment (UE), comprising: Determine to enter a two-step random access channel (RACH) procedure in a radio resource control (RRC) inactive state; Determining that uplink data is transmitted in the payload of message A MsgA of the two-step RACH procedure; transmitting a MsgA of the two-step RACH procedure, wherein the MsgA includes the payload, and the payload includes at least the uplink data; Monitoring message B MsgB of the two-step RACH procedure; retransmitting the MsgA when the MsgB is not received within a configured time window, the retransmitted MsgA including a payload and a preamble, wherein the payload of the retransmitted MsgA includes at least one of an RRC message or a data request message; as well as receiving a second MsgB in response to retransmitting the MsgA, the second MsgB including pre-configured uplink resources to enable transmission of subsequent uplink data without entering an RRC_CONNECTED state, One or more new preamble groups are selected for the retransmitted MsgA, wherein the one or more new preamble groups are mapped to physical uplink shared channel resources with larger uplink granted resources. 15 . The method of claim 14 , wherein a payload of the MsgA comprises at least one of an RRC message or a data request message, the MsgA comprising a preamble associated with one of one or more preamble groups.

16. The method of claim 14, further comprising: A MsgB of the two-step RACH procedure is received, wherein the MsgB includes a fallback indication, and the fallback indication includes a fallback random access response RAR.

17. The method of claim 16, further comprising: retransmitting the payload of the MsgA when the MsgB including the backoff indication is received.

18. The method of claim 16, further comprising: After receiving the MsgB including the backoff indication, a message 3 Msg3 is transmitted, wherein hybrid automatic repeat request HARQ retransmission is applied to Msg3.

19. An apparatus for wireless communication of a user equipment (UE), comprising: means for determining to enter a two-step random access channel (RACH) procedure in a radio resource control (RRC) inactive state; means for determining to transmit uplink data in a payload of message A MsgA of a two-step RACH procedure; means for transmitting a MsgA of the two-step RACH procedure, the MsgA comprising the payload, the payload comprising at least the uplink data; means for monitoring message B MsgB of said two-step RACH procedure; means for retransmitting the MsgA when the MsgB is not received within a configured time window, the retransmitted MsgA comprising a payload and a preamble, wherein the payload of the retransmitted MsgA comprises at least one of an RRC message or a data request message; as well as means for receiving a second MsgB in response to retransmitting the MsgA, the second MsgB including pre-configured uplink resources to enable transmission of subsequent uplink data without entering an RRC_CONNECTED state, One or more new preamble groups are selected for the retransmitted MsgA, wherein the one or more new preamble groups are mapped to physical uplink shared channel resources with larger uplink granted resources.

20. A computer-readable medium having instructions stored thereon, which, when executed by a processor, cause the processor to perform the method of any one of claims 14-18.

21. A computer program product comprising computer instructions which, when executed by a processor, cause the processor to perform the method of any one of claims 14 to 18.

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